Title of Invention	A TWO WIRE COMMUNICATION SYSTEM.
Abstract	TITLE: A TWO WIRE COMMUNICATION SYSTEM. A two wire communication system capable of transmitting data and transferring power by means of an electrical bi-polar waveform across a two wire conductor from a controller in communication with said two-wire conductor to at least one module in communication with said controller and capable of transmitting data from said at least one module to said controller; the system comprising a remote electrical device in communication with said controller; characterized in that the system is capable of continuous transmission of usable data across said two wire conductor independent of and during power transmission between said controller and said at least one module without loss of data transmission time and without affecting the transfer of power to said at least one module.

Title of Invention

A TWO WIRE COMMUNICATION SYSTEM.

Abstract

TITLE: A TWO WIRE COMMUNICATION SYSTEM. A two wire communication system capable of transmitting data and transferring power by means of an electrical bi-polar waveform across a two wire conductor from a controller in communication with said two-wire conductor to at least one module in communication with said controller and capable of transmitting data from said at least one module to said controller; the system comprising a remote electrical device in communication with said controller; characterized in that the system is capable of continuous transmission of usable data across said two wire conductor independent of and during power transmission between said controller and said at least one module without loss of data transmission time and without affecting the transfer of power to said at least one module.

Full Text	BACKGROUND The present invention relates to the field of data communication systems and to distributed two wire communication systems. More particularly the invention relates to a two wire communication system utilising a communication protocol in which an electrical bi - polar waveform is used for data transmission and power transfer over a two wire conductor system. The protocol is a physical layer protocol which defines the electrical waveform applied to a two wire conductor system acting as the transmission means The two wire conductor system is used to interconnect a Controller and at least one module but preferably a multiplicity of modules Throughout the specification the term Controller will be used to describe a device which controls the two wire conductor and the term Module will be used to describe a device which connects to the two wire conductor. In operation the communication protocol allows data communication between the Controller and the Modules across the two wire conductor by a digital communication methodology which is provided by the bi - polar waveform structure as defined in the protocol Power transfer via the two wire conductor from the controller to the modules is also achieved by the bi - polar waveform structure as defined by the protocol PRIOR ART Two wire conductor systems are known in the electrical engineering and electronics fields as a means of data and power transmission Systems of this type generally known as Down Line Powered two wire conductor communication system (DLPCS) typically employ a controller which drives power into the two wire conductor systems, controls the timing of data transfer and transmits and receives data They also employ modules which draw power from the two wire conductoi and transmit and receive data DLPCS"s can be classified into uni - polar DLPCS"s and bi - polar DLPCS"s Most data and power transmission systems use different conductors for the transmission of data and the transmission of power However, in low power applications where the length of the conductors between the Modules and the Controller is large, the transfer of power and data over the same two conductors can give large cost savings compared with multiple conductor systems A unipolar DLPCS is a system where the Controller drives power down the two wire conductor using one voltage polarity Data is transferred between the Controller and Modules by modulating the voltage ( between voltages of the same polarity ) and current ( positive or negative ) Power can be transferred from the Controller to the Modules while ever the line voltage are higher than the internal voltage of the Modules A telephone system is an example of a uni polar DLPCS wherein power is drawn continuously from the line by the telephone which transmits the voice signal by modulating the telepohone"s impedance The change of impedance modulates the voltage and current on the two wire communication line. Digital data transfer via the telephone DLPCS usually requires special modulation techniques using modems Another uni-polar DLPCS provides for a controller and multiple modules connected to a two-wire line and supports digital data only. The modules draw power whenever the voltage is high Digital data is transmitted and received by the modules during periods when the voltage on the two -wire line is "low" The controller lengthens the "low" voltage period if a low impedance is detected across the two-wire line Modules transmit data by modulating their impedance in the "low" voltage periods An advantage of this signalling technique is that all modules connected to the two wire line receive all data transmitted over the two wire line Module to module communication is also possible The "low" voltage disables power transmission so the controller can easily detect the data signal A disadvantage of this approach is that the low1 voltage has a low noise margin ( the amount of noise voltage that is needed to corrupt the data) Another disadvantage is thai it is difficult to adjust the speed of operation to accommodate different operational environments Another two wire utility data communication system for communicating utility meter readings over two wires is disclosed in Australian patent application 64664/94 The specification teaches communication systems used to transmit consumption data from a meter such as an electric, gas or water meter to remote meter reading units The system described is very similar to a well known field known as M-BUS and provides for a controller and multiple modules connected to a two- wire line The invention described comprises a reader /programmer for communicating with a utility meter or the like over at least two- wire lines. The system described includes means for generating an interrogate signal, means for demodulating a data signal received from the utility meter over the two- wire lines wherein the data signal consists of a current in the two-wire lines which varies in accordance with data being transmitted from the utility meter when the leader/programmer is connected via two wire lines and means for demodulating the data signal received from the utility meter over the wire lines wherein the data signal has characteristics which vary in accordance with the data being transmitted from the utility metel Each meter includes an encoder which converts consumption information displayed by a mechanical or electronic register associated with the meter to a form which can be transmitted over wires or the like to a remotely located meter reading unit The specification also teaches the use of three wire communications for the system When operating in the two wire mode the reader/programmer and encoder are inductively coupled The encoder includes circuitry for varying an impedance in accordance with data representing the quantity being measured by the meter to cause the current flowing between the encoder and the remote reader/programmer to be modulated in accordance with the data The system is relatively complicated in the coding and decoding of the signals in comparison to pulse duration signals and furthermore it does not permit use of 100% of data transmission time when transmitting power due to the nature of the uni-polar signalling used to transmit both power and data. The modules draw power while ever the voltage is "high" The controller transmits binary data to the modules by modulating the voltage between "high" and zero voltage The modules transmit data to the controller by modulating the line current on the two- wire line by varying the modules"s impedance. This system works well when the module"s dala current is much larger than the power consumption current It is therefore a disadvantage that power consumption is limited Another disadvantage of this system is that modules can only receive data from the controller Also the communication speed can be adjusted to meet unusual operating conditions but the speed is generally limited to fixed baud rates and it is difficult to change baud rates during operation Another known digital uni-polar DLPCS employs said two- wire protocol wherein the modules draw power when the voltage is high In that system the controller transmits data to the modules by modulating the voltage between "high" and zero voltage The modules transmit data to the controller by modulating their impedance which modulates the line voltage and current In this case all modules connected to the line can receive all data transmitted on the two- wire line as the modules modulate the voltage between "high" and near zero voltage. The key disadvantage of this " system is that very little power can be transmitted and communication speed has to be fixed Bi-polar DLPCS"s are systems where the controller drives power down the two wire conductor using an alternating voltage polarity Data is transmitted between the controller and modules by modulating the voltage and /or current The module"s circuitry whtch draws power from the line and enables data transfer by modulation of the voltage oi the current, is more complex than the uni-polar interface circuitry of the DLPCS Bi-polar systems have a number of advantages including the ability to detect a change of polarity more reliably and with less circuitry than a voltage level in the uni-polar systems A further advantage is that the bi-polar system has twice the noise margin of a uni polar system for a given line voltage Another advantage is that power transmission can occur during either polarity. The bi-polar signal supports binary communication, and low voltage periods, as in some uni polar systems, can be eliminated Australian patent 481585 (82170/75) discloses a signal transmission system for telemetering instruments and controllers in a process control system. It is an object of the invention described in that patent to provide a signal transmission system capable of transmitting data in terms of pulse duration together with power necessary to operate process instruments The patent teaches that data transmission and power transmission are carried out alternately by changing the polarity of the line voltage It is a further object of the invention disclosed in that patent to provide a signal transmission system capable of analogue -to - digital and digital -to - analogue conversion for signal transmission The system described is complex in that it employs diodes including a photocoupler which allow current to flow forward and which are capable of detecting the flow of current As part of its operation, a signal start drives a converter so that process data is converted into a pulse width proportional to its analogue value The patent teaches signal transmission and power transmission earned out alternately by changing the polarity of the loop current Alternatively, the value of current , the polarity of voltage or the value of voltage may be changed to set up transmission systems for signal and power instead of proportional relationship between pulse width and analogue value a logararithinic . exponential, square or like relationship may be used for the two signals During data transmission, the controller modulates the data pulse duration in response to a change of impedance caused by the modules This has the advantage that all modules can receive all data transmitted on the line The key disadvantage of this system is that no useful information is transmitted during the power period, wasting a significant percentage of the available transmission communication time Furthermore, there is no means to enable the transmission of power during the data periods when the controller is the originator of the data The system described is said to be readily compatible with digital systems as well as analogue systems The primary disadvantage of the system described in that patent is that during periods of power transmission no useful data transmission can occur Another known two wire system is described in Japanese publication No.5003457 but this arrangement also suffers from the disadvantage that data transmission time is compromised during power transmission In fact a significant amount of time is devoted to power transmission which prevents data transmission during that period The prior art arrangements for transmitting data and power over the same two wires are disadvantaged by the fact that they devote a percentage of the total transmission time to the transfer of power during which phase no useful data is transmitted According to the prior art methodology, up to 50% of the available transmission time is used for transferring power to modules Furthermore, all uni-polar prior art systems have much smaller noise margins and so are more susceptible to noise on long distance transmission Another prior art in digital bi-polar DLPCS involves power and data transmission by the controller to the modules at a "high" bi-polar voltage and the modules respond using a low bi-polar voltage In this system high communication speeds are possible The "low" voltage transmission in this case can be made robust in the presence of noise because the modules directly drive the line voltages The disadvantage of this approach is that the modules use significant power whenever they transmit data and the length of time that can expire between power transmissions from the controller necessitates large energy storage devices in all modules Up until the present, the art has not included a system which modulates the pulse duration of both polarities with data and allows power to be drawn from either polarity depending on the data being transmitted. It is now possible using this system to power and communicate with hundreds possibly thousands of modules on a low cost cable Whilst the industry has been well served by standard communication techniques where power and data are run in separate cables there has been a long felt want for a system which enables communication and power transmission over long distances say greater than 5 kilometers and particularly in environments where power voltage and current must be kept at low levels for safety reasons but without compromise to data transmission time Such a system can be used to advantage in explosive mining environments where long distances require increased power transmission but regulation requires a power not to exceed a predetermined maximum and where data transmission is desirable 100° c of the time THE INVENTION The present invention seeks to overcome theaforesaid prior art disadvantages by providing a two wire communication system in which data and power are transferred over the same two wires using a bi-polar signal such that useful data can be transmitted independant of and during power transmission without loss of data transmission time According to the invention 100% of the transmission time is used in data transmission without affecting the transfer of power to the modules connected to the two wire conductor According tc the prior art in comparison, up to 50% of transmission time may be lost in transfering power to the modules The arrangement of the present invention utilises a bi-polar signal which has a very large noise margin As each period is followed by a period of the opposite polarity and only one value (analogue or digital) is conveyed during each period, there is no fixed timing with respect to data Also, the line speed can be increased or decreased at an arbitrary baud rate, because timing information for data sampling is passed with each transition of the polarity Further, the arrangement of the invention can support full duplex protocols on a single two wire conductor system The protocol supports two data channel for simultaneous independent data transmission in both directions. It is one object of the invention to provide a two wire communication protocol for a communication system which is capable of transmitting data in terms of pulse duration together with power to at least one but preferably a multiplicity of modules connected to the two- wire conductor wherein useful data may be sent 100% of the time and allow the designer to specifiy the power duty cycle required for the application In one broad form the present invention comprises a two wire communication system capable of transmitting data and transferring power by means of an electrical bi-polar waveform across a two wire conductor from a controller in communication with said conductor to at least one module in communication with said controller and/or data from said at least one module to said controller, the system including a remote electrical device in communication with said controller, wherein useable data may be continuously transmitted across said two wire conductor independent of and during power transmission between said controller and said at least one module without loss of data transmission time and without affecting the transfer of power to said at least one module In another broad form the present invention comprises a two wire communication system capable of transmitting data and transferring power by means of an electrical bi-polar waveform across a two wire conductor From a controller in communication with said conductor to at least one module in communication with said controller and/or data from said at least one module to said controller, the two wire system including a remote electrical device in communication with said controller, wherein useable data may be continuously transmitted across said two wire conductor independant of and during power transmission between said controller and said at least one module without loss of data transmission time and without affecting the transfer of power to said at least one module; wherein the system is capable of using up to 100% of available transmission time to transmit data without affecting transfer of power to said at least one module, and wherein data and power transfer are effected through the same transmission line According to a preferred embodiment a plurality of modules are connected in parallel and which are each capable of transmitting and receiving data across said conductor Preferably, when the controller is transmitting data said modules are capable of drawing power and when each said modules transmit data they do not draw power from said controller nor from other modules Each module is capable of transmitting data by putting a low impedance signal across said two wire conductor wherein, said low impedance signal from said module for data transmission does not distort pulse duration allowing said controller to transmit data on the two-wire transmission line to any value independant of said impedance signal from each module The low impedance signal may convey analogue or digital information by either modulating the current, voltage or duration of said low impedance signal In a further broad form the present invention comprises, a two- wire communication system for transmitting power and data between a controller and at least one module, said system including a two wire transmission line including two data channels which allow two independant bi -directional communication channels between the controller and said at least one module wherein power may be drawn by said at least one module whilst ever the controller is transmitting data on either data channel, wherein when said module is transmitting data back to the controller no power transfer is possible to other modules In another broad form the present invention comprises a two wire communication system for transmitting power and data between a controller and at least one module, said system including a two wire transmission conductor including two data channels which allow two independant bi directional communication channels between the controller and said at least one module wherein power may be drawn by said at least one module whilst ever the controller is transmitting data on either data channel, wherein when said module is transmitting data back to the controller no power transfer is possible to other modules, wherein the system includes a P-side channel allowing bi-directional data flow and power transfer from said controller to said at least one module and an N- side channel allowing bi-directional data flow and power transfer between the controller and said at least one module, wherein, when data is transmitted on said P- side channel, said controller modulates at the P- side pulse width to effect data transfer such that the system is capable of utilising up to 100% of the transmission time to transmit data without affecting the transfer of power across said two wire transmission conductor According to a preferred embodiment there is provided means at the controller and modules to convey data to connect remote electrical devices and receive data from said connected remote electrical devices According to the preferred embodiment there are a plurality of sparsely separated modules connected in parallel across said conductor along with one controller which i: connected in parallel across said two- wire conductor. Preferably a bi-polar signalling scheme is used which provides high noise immunity The two polarities of the two wire conductor are designated P -side and N-side, wherein, the pulse width of the P-Side pulses and N-side pulses are modulated by the controller to convey all data to all modules connected to the two-wire conductor Preferably, all modules connected to the conductor can take power from the conductor when the controller is transmitting data The relative duration of the controller data compared with the module data determines the power duty cycle for the conductor Preferably, the power available to the modules connected to the conductor can be traded off against communication speed Modules connected to the conductor can pass data to the controller by putting low impedance across the conductor The controller can then modulate the duration pf the pulse in response to the low impedance signal from the module The low impedance signal from the module does not distort the duration of the pulse directly, so the controller can still force data on the conductor ro any desired value independently of the modules low impedance signal Further, the module"s low impedance signal may convey analogue or digital information by either modulating the current, voltage or duration of the low impedance signal. Accordingly, the present invention provides a two wire communication system capable of transmitting data and transferring power by means of an electrical bi-polar waveform across a two wire conductor from a controller in communication with said two-wire conductor to at least one module in communication with said controller and capable of transmitting data from said at least one module to said controller; the system comprising a remote electrical device in communication with said controller; wherein the system is capable of continuous transmission of usable data across said two wire conductor independent of and during power transmission between said controller and said at least one module without loss of data transmission time and without affecting the transfer of power to said at least one module. The present invention also provides a two wire communication system capable of transmitting data and transferring power by means of an electrical bi-polar waveform across a two wire conductor from a controller in communication with said two-wire conductor to at least one module in communication with said controller and capable of transmitting data from said at least one module to said controller; and a remote electrical device in communication with said controller; wherein useable data may be continuously transmitted across said two wire conductor independent of and during power transmission between said controller and said at least one module without loss of data transmission time and without affecting the transfer of power to said at least one module; wherein, said data is transmitted across said two wire conductor to said modules by pulse duration signals at the same time power is transmitted to said modules; wherein the system is capable of using up to 100% of transmission time to transmit data without affecting transfer of power to said at least one module. The present invention will now be described according to a preferred but non limiting embodiment and with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1 is a block diagram of an overview of the system according to one embodiment of the invention. Figure 2 is a block diagram of the controller according to one embodiment of the invention. Figure 3 is a block diagram of the module according to one embodiment of the invention; and, Figure 4 is a block diagram of a P-Side N- side line protocol according to a preferred embodiment of the invention. Figure 5 shows a schematic example of a system arrangement involving monitoring of emergency stop switches; and Figure 5a shows the arrangement of figure 5 with one emergency stop switch operated. DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION The DLPCS according to the invention was developed for use in particular, though not exclusively in long distance mining operations where explosive atmospheres require that power voltages and current be kept to safe minimums. Due to large power and data transmission distances in mining applications constraints on transmission of power would normally compromise data transmission. These constraints are not an issue in relatively short distance communications in normal above ground operations presently satisfied by prior art technology. A preferred embodiment of the invention is shown in Figure 1 and comprises a schematic layout of the two wire communication system. The system shown comprises a controller 1 including means to receive inputs 2 and deliver outputs 3 and in communication with a first end 4 of a two ------------------------------------------------------ wire conductor 5 comprising an L+ wire and an L- wire The system further comprises a multiplicity of modules 6, 7 and 8 each remote from one another and which are in communication^ with said L+ and L- wires such that each module is in communication with controller 1 and in communication with each other module The system is such that data can be transmitted from the controller 1 onto the transmission line L+and L- and received at said modules 6, 7 and 8 Data can also be transmitted from any one module 6, 7 and 8 onto the transmission lines L+ and L- and received at the controller 1 and at any one of the remaining multiplicity of modules By means of connection inputs and outputs 2 and 3, data is transferred between remote electrical devices and the controller 1 Figure 2 shows a controller according to a preferred embodiment. The controller includes a power supply 13 which converts high voltage power to low voltage power levels appropriate for the chosen application Processor 14 is programmed to effect all the conrrol and timing functions inside the controller Remote electrical devices are connected to the controller via Inputs and Outputs 12 The bi-polar driver 1 1 is a controllable power source which can drive power into the conductors L+ and L- in a negative polarity The current being drawn bv modules connected to the two wire !ineL+ and L- is monitored by current measurement 10. The voltage on the line L+ and L- is measured by voltage measurement 9 Figure 3 shows a block diagram of the module according to one embodiment of the invention. The module includes power supply voltage regulator 1 7, storage capacitor 20 and steering diode 2 1 The module"s reply circuitry comprises Level Shift 18, reply transistor 23 and steering diode 22 Data and timing is taken from receive clock 19 The processor 25 is programmed to effect all the control and timing functions inside the module Remote electrical devices are connected to the module via inputs and outputs 24 Figure 4 shows a block diagram of a P-Side N- side line protocol according to a preferred embodiment of the invention The P-side channel and the N- side communication channels are bi directional communication channels between the controller and the modules 6, 7 and 8. When transmitting data on the P- side channel the controller 1 modulates the P- side pulse width to effect data transfer According to the preferred embodiment of the invention, three symbols are used to effect data transfer on the P-side, namely a synchronous pulse 46, a zero pulse 44 and a one pulse 45 A reply pulse 48 has the same period as a one pulse 45 The period of the synchronous pulse 46 is longer than the one pulse 45 The one pulse 45 is longer than the zero pulse 44 A synchronous pulse 46 alerts all modules connected to the line that new data follows The digital data in the new data to be transmitted is represented by zero pulses 44 and one pulse 45 If the controller wants to transmit data on the P- side channel it transmits Zero pulses 44 and one pulses 45 according to the digital data being transmitted If a module is transmitting data on the P- side channel the controller issues a zero pulse 44 and modulates rhe period to a one pulse 45 if a low impedance is measured during the zero pulse 44 When a low impedance is placed on the two wire conductor by a module the line voltage is reduced and line current is increased as in the reply pulse 48 When transmitting data on the N- side channel the controller modulates the side pulse width to effect data transfer According to the preferred embodiment of the invention , three symbols are used to effect data transfer on the Signal side , a synchronous pulse 47, a zero pulse 41 and a one pulse 42 A reply pulse 43 has the same period as a one pulse 42 The period of the synchronous pulse 47 is longer than the one pulse 42 The one pulse 42 is longer than the zero pulse 41 The controller transmits a synchronous pulse 47 to alert all modules connected to the line that new data follows The digital data to be transmitted is represented by zero pulses 41 and one pulses 42 If the controller wants to transmit data on the N- side channel it transmits Zero pulses 41 and one pulses 42 according to the digital data being transmitted If a module is transmitting data on the N- side channel the controller issues a zero pulse 41 and modulates the period to a one pulse 42 if a low impedance is measured during the zero pulse 41 When a low impedance is placed on the two wire conductor by a module the line voltage is reduced and line current is increased as in the reply pulse 43 The controller reads the current measurement 12 and voltage " measurement 11 to determine if a module is placing a low impedance on the conductor and modulates the period to the same length of a one pulse 42 if a low impedance is detected If there is no reply from a module connected to the conductor the controller terminates the pulse when it is equal to a zero pulse 41 In the foregoing embodiment, digital data is transferred over the P- side channel and the signal N- side channel. A higher level protocol enables addressing and arbitration between modules so individual modules can be individually accessed However it is clear that many high level protocols including full duplex communication can be supported using the two communication channels on the P- side and N- side It is also clear that the pulse period can be modulated with analogue data instead of the digital modulation used in the foregoing embodiment In fact, any number of pulse symbols and analogue modulation of the pulse period could be supported under a high level protocol Refering to figure 5 there is shown an example of the use of a system in accordance with the present invention The system shown is applicable to transmission of data relating to a conveyor belt used for example in mining operations particularly though not exclusively where communications over 5 kilometers is required and where the potentially explosive atmospheres common in mining, limits the energy that may be applied to wire conductors to avoid ignition of explosive gas The system includes a controller 50 linked to one end of a two wire communication line 5 1 and at the other end, to an end of line module 52 The system further comprises a plurality of additional modules 53, 54, 55, 56 and 57, connected in parallel and in electrical communication with respective associated switches 58, 59, 60, 61 and 62 In accordance with the system set up, the emergency switches are monitored for correct Operation and should any one of switches 58, 59, 60, 61 and 62 be operated the end of line module 52 will be open circuit and will go off line in view of the series connection with module 52 Each emergency stop switch has two contacts which are operated simultaneously should the emergency stop switch be operated The second of the two contacts is monitored by the modules 53, 54, 55, 56 and 57 allowing the modules to report back to the controller on which emergency switch has been operated Figure 5a shows the arrangement of figure 5 wherein emergency switch 60 has been operated. Two wire communication line is now open at module 55 rendering modules 56 and 57 to be off line Module 55 will send data backto controller 50 indicating that it"s emergency switch 60 has been operated While a preferred embodiment has been described , it is understood that numerous variations anc modifications may occur to those skilled in the art without departing from the overall spirit and scope of the invention WE CLAIM : 1. A two wire communication system capable of transmitting data and transferring power by means of an electrical bi-polar waveform across a two wire conductor from a controller in communication with said two-wire conductor to at least one module in communication with said controller and capable of transmitting data from said at least one module to said controller; the system comprising a remote electrical device in communication with said controller; wherein the system is capable of continuous transmission of usable data across said two wire conductor independent of and during power transmission between said controller and said at least one module without loss of data transmission time and without affecting the transfer of power to said at least one module. 2 A two wire communication system capable of transmitting data and transferring power by means of an electrical bi-polar waveform across a two wire conductor from a controller in communication with said two-wire conductor to at least one module in communication with said controller and capable of transmitting data from said at least one module to said controller; and a remote electrical device in communication with said controller; wherein useable data may be continuously transmitted across said two wire conductor independent of and during power transmission between said controller and said at least one module without loss of data transmission time and without affecting the transfer of power to said at least one module; wherein, said data is transmitted across said two wire conductor to said modules by pulse duration signals at the same time power is transmitted to said modules; wherein the system is capable of using up to 100% of transmission time to transmit data without affecting transfer of power to said at least one module. 3. A two wire communication system as claimed in claim 1, wherein said data is transmitted across said two wire conductor to said at least one modules by pulse duration at the same time power is transmitted to said modules. 4. A two wire communication system as claimed in claim 2 or 3, wherein data and power transfer are effected through the same transmission line. 5. A two wire communication system as claimed in claim 4, wherein a plurality of modules are connected in parallel and which are each capable of transmitting and receiving data across said conductor. 6. A two wire communication system as claimed in claim 5, wherein when the controller is connected in parallel across the conductor. 7. A two wire communication system as claimed in claim 6, wherein said at least one modules are capable of drawing power when the controller is transmitting data. 8. A two wire communication system as claimed in claim 7, wherein when each said at least one modules transmit data they do not draw power from said controller nor from other modules. 9. A two wire communication system as claimed in claim 8, wherein each module is capable of transmitting data by putting a low impedance signal across said two wire conductor. 10. A two wire communication system as claimed in claim 9, wherein said low impedance signal from said at least one module for data transmission does not distort pulse duration allowing said controller to transmit data on the two wire conductor to any value independent of said impedance signal from each module. 11 A two wire communication system claim 10, wherein said low impedance signal may convey analogue or digital information by either modulating the current, voltage or duration of said low impedance signal. 12. A two wire communication system as claimed in claim 11, wherein the two wire conductor have polarities designated as first and second channels the first of which is a P-side channel allowing bi-directional data flow and power transfer and the second of which is an N-side channel allowing bi-directional data flow and power transfer. 13. A two wire communication system as claimed in claim 12, wherein said first P- side channel allows two way communication between said controller and said at least one modules. 14. A two wire communication system as claimed in claim 13, wherein; said second N-side channel allows two way communication between said controller and said at least one modules. 15. A two wire communication system as claimed in claim 14, wherein pulse widths of the P-side channel are modulated by the controller to convey all data to all modules connected to the two way conductor. 16. A two wire communication system as claimed in claim 15, wherein the pulse widths of the N-side channel are modulated by the controller to convey all data to all modules connected to the two wire conductor. 17. A two wire communication system as claimed in claim 16, wherein data is transferred between the controller and said plurality of modules by modulation of the pulse width of the P-side and N-side pulses. 18. A two wire communication system as claimed in claim 17, wherein the P-side channel is independent of the N- side communication channel. 19. A two wire communication system as claimed in claim 18, wherein data is transmitted on the P-side channel by modulation of the P-side pulse width. 20. A two wire communication system as claimed in claim 19, wherein power may be taken from the two wire conductor during either N-side or P-side polarities whilst ever said controller transmits data. 21. A two wire communication system as claimed in claim 20, wherein there is provided means at the controller to measure the voltage of the conductor and the current into the conductor such that low impedance replies from modules are detected. 22. A two wire communication system as claimed in claim 21, wherein there is provided means at the controller to control the duration of the power source in either polarity, wherein the duration of the power transmission is represented in an analogue or digital value. 23. A two wire communication system as claimed in claim 22, wherein there is provided at said module means to sense the polarity of the conductor and measure the duration of transmission in either polarity. 24. A two wire communication system as claimed in claim 23, wherein there is provided means at the module to receive power from the conductor. 25. A two wire communication system as claimed in claim 24, comprising means at the controller and modules to convey data to and receive data from connected remote electrical devices. 26. A two wire communication system as claimed in claim 25, wherein there is provided means at said at least one modules to reply on said conductor by placing a low impedance across said conductor; wherein, said controller can modulate duration of pulse in response to said low impedance signal from said module. 27 A two wire communication system as claimed in claim 26, wherein the controller has therewithin a power source which can be impressed on the conductor in a positive or negative polarity. 28. A two wire communication system, substantially as herein described, particularly with reference to and as illustrated in the accompanying drawings. A two wire communication system capable of transmitting data and transferring power by means of an electrical bi-polar waveform across a two wire conductor from a controller (1) in communication with said two-wire conductor to at least one module (6, 7, 8) in communication with said controller and capable of transmitting data from said at least one module to said controller (1); the system comprising a remote electrical device in communication with said controller (1) ; characterized in that the system is capable of continuous transmission of usable data across said two wire conductor independent of and during power transmission between said controller (1) and said at least one module (6, 7, 8) without loss of data transmission time and without affecting the transfer of power to said at least one module (6, 7, 8).

Full Text

BACKGROUND
The present invention relates to the field of data communication systems and to distributed two
wire communication systems. More particularly the invention relates to a two wire
communication system utilising a communication protocol in which an electrical bi - polar
waveform is used for data transmission and power transfer over a two wire conductor system.
The protocol is a physical layer protocol which defines the electrical waveform applied to a two
wire conductor system acting as the transmission means The two wire conductor system is used
to interconnect a Controller and at least one module but preferably a multiplicity of modules
Throughout the specification the term Controller will be used to describe a device which controls
the two wire conductor and the term Module will be used to describe a device which connects to
the two wire conductor. In operation the communication protocol allows data communication
between the Controller and the Modules across the two wire conductor by a digital
communication methodology which is provided by the bi - polar waveform structure as defined in
the protocol Power transfer via the two wire conductor from the controller to the modules is
also achieved by the bi - polar waveform structure as defined by the protocol
PRIOR ART
Two wire conductor systems are known in the electrical engineering and electronics fields as a
means of data and power transmission Systems of this type generally known as Down Line
Powered two wire conductor communication system (DLPCS) typically employ a controller
which drives power into the two wire conductor systems, controls the timing of data transfer and
transmits and receives data
They also employ modules which draw power from the two wire conductoi and transmit and

receive data DLPCS"s can be classified into uni - polar DLPCS"s and bi - polar DLPCS"s
Most data and power transmission systems use different conductors for the transmission of data
and the transmission of power However, in low power applications where the length of the
conductors between the Modules and the Controller is large, the transfer of power and data over
the same two conductors can give large cost savings compared with multiple conductor systems
A unipolar DLPCS is a system where the Controller drives power down the two wire conductor
using one voltage polarity Data is transferred between the Controller and Modules by modulating
the voltage ( between voltages of the same polarity ) and current ( positive or negative ) Power
can be transferred from the Controller to the Modules while ever the line voltage are higher than
the internal voltage of the Modules
A telephone system is an example of a uni polar DLPCS wherein power is drawn continuously
from the line by the telephone which transmits the voice signal by modulating the telepohone"s
impedance The change of impedance modulates the voltage and current on the two wire
communication line. Digital data transfer via the telephone DLPCS usually requires special
modulation techniques using modems
Another uni-polar DLPCS provides for a controller and multiple modules connected to a
two-wire line and supports digital data only. The modules draw power whenever the voltage is
high Digital data is transmitted and received by the modules during periods when the voltage on
the two -wire line is "low" The controller lengthens the "low" voltage period if a low impedance
is detected across the two-wire line Modules transmit data by modulating their impedance in the
"low" voltage periods An advantage of this signalling technique is that all modules connected to
the two wire line receive all data transmitted over the two wire line Module to module
communication is also possible The "low" voltage disables power transmission so the controller
can easily detect the data signal A disadvantage of this approach is that the low1 voltage has a
low noise margin ( the amount of noise voltage that is needed to corrupt the data) Another
disadvantage is thai it is difficult to adjust the speed of operation to accommodate different
operational environments
Another two wire utility data communication system for communicating utility meter readings
over two wires is disclosed in Australian patent application 64664/94 The specification teaches
communication systems used to transmit consumption data from a meter such as an electric, gas
or water meter to remote meter reading units The system described is very similar to a well
known field known as M-BUS and provides for a controller and multiple modules connected to a
two- wire line The invention described comprises a reader /programmer for communicating with
a utility meter or the like over at least two- wire lines. The system described includes means for
generating an interrogate signal, means for demodulating a data signal received from the utility
meter over the two- wire lines wherein the data signal consists of a current in the two-wire lines
which varies in accordance with data being transmitted from the utility meter when the
leader/programmer is connected via two wire lines and means for demodulating the data signal
received from the utility meter over the wire lines wherein the data signal has characteristics
which vary in accordance with the data being transmitted from the utility metel
Each meter includes an encoder which converts consumption information displayed by a
mechanical or electronic register associated with the meter to a form which can be transmitted
over wires or the like to a remotely located meter reading unit The specification also teaches the
use of three wire communications for the system When operating in the two wire mode the
reader/programmer and encoder are inductively coupled
The encoder includes circuitry for varying an impedance in accordance with data

representing the quantity being measured by the meter to cause the current flowing between the
encoder and the remote reader/programmer to be modulated in accordance with the data
The system is relatively complicated in the coding and decoding of the signals in comparison to
pulse duration signals and furthermore it does not permit use of 100% of data transmission time
when transmitting power due to the nature of the uni-polar signalling used to transmit both power
and data. The modules draw power while ever the voltage is "high" The controller transmits
binary data to the modules by modulating the voltage between "high" and zero voltage The
modules transmit data to the controller by modulating the line current on the two- wire line by
varying the modules"s impedance. This system works well when the module"s dala current is
much larger than the power consumption current It is therefore a disadvantage that power
consumption is limited Another disadvantage of this system is that modules can only receive data
from the controller Also the communication speed can be adjusted to meet unusual operating
conditions but the speed is generally limited to fixed baud rates and it is difficult to change baud
rates during operation
Another known digital uni-polar DLPCS employs said two- wire protocol wherein the modules
draw power when the voltage is high In that system the controller transmits data to the modules
by modulating the voltage between "high" and zero voltage The modules transmit data to the
controller by modulating their impedance which modulates the line voltage and current In this
case all modules connected to the line can receive all data transmitted on the two- wire line as the
modules modulate the voltage between "high" and near zero voltage. The key disadvantage of this "
system is that very little power can be transmitted and communication speed has to be fixed
Bi-polar DLPCS"s are systems where the controller drives power down the two wire conductor
using an alternating voltage polarity

Data is transmitted between the controller and modules by modulating the voltage and /or current
The module"s circuitry whtch draws power from the line and enables data transfer by modulation
of the voltage oi the current, is more complex than the uni-polar interface circuitry of the DLPCS
Bi-polar systems have a number of advantages including the ability to detect a change of
polarity more reliably and with less circuitry than a voltage level in the uni-polar systems A
further advantage is that the bi-polar system has twice the noise margin of a uni polar system for a
given line voltage Another advantage is that power transmission can occur during either polarity.
The bi-polar signal supports binary communication, and low voltage periods, as in some uni polar
systems, can be eliminated
Australian patent 481585 (82170/75) discloses a signal transmission system for telemetering
instruments and controllers in a process control system. It is an object of the invention described
in that patent to provide a signal transmission system capable of transmitting data in terms of
pulse duration together with power necessary to operate process instruments The patent teaches
that data transmission and power transmission are carried out alternately by changing the polarity
of the line voltage It is a further object of the invention disclosed in that patent to provide a
signal transmission system capable of analogue -to - digital and digital -to - analogue conversion
for signal transmission
The system described is complex in that it employs diodes including a photocoupler which allow
current to flow forward and which are capable of detecting the flow of current As part of its
operation, a signal start drives a converter so that process data is converted into a pulse width
proportional to its analogue value The patent teaches signal transmission and power transmission
earned out alternately by changing the polarity of the loop current Alternatively, the value of
current , the polarity of voltage or the value of voltage may be changed to set up transmission

systems for signal and power instead of proportional relationship between pulse width and
analogue value a logararithinic . exponential, square or like relationship may be used for the two
signals During data transmission, the controller modulates the data pulse duration in response to
a change of impedance caused by the modules This has the advantage that all modules can
receive all data transmitted on the line
The key disadvantage of this system is that no useful information is transmitted during the power
period, wasting a significant percentage of the available transmission communication time
Furthermore, there is no means to enable the transmission of power during the data
periods when the controller is the originator of the data The system described is said to be
readily compatible with digital systems as well as analogue systems
The primary disadvantage of the system described in that patent is that during periods of power
transmission no useful data transmission can occur
Another known two wire system is described in Japanese publication No.5003457 but
this arrangement also suffers from the disadvantage that data transmission time is compromised
during power transmission In fact a significant amount of time is devoted to power transmission
which prevents data transmission during that period
The prior art arrangements for transmitting data and power over the same two wires are
disadvantaged by the fact that they devote a percentage of the total transmission time to the
transfer of power during which phase no useful data is transmitted According to the prior art
methodology, up to 50% of the available transmission time is used for transferring power to
modules Furthermore, all uni-polar prior art systems have much smaller noise margins and so are
more susceptible to noise on long distance transmission
Another prior art in digital bi-polar DLPCS involves power and data transmission by the

controller to the modules at a "high" bi-polar voltage and the modules respond using a low
bi-polar voltage In this system high communication speeds are possible The "low" voltage
transmission in this case can be made robust in the presence of noise because the modules directly
drive the line voltages The disadvantage of this approach is that the modules use significant
power whenever they transmit data and the length of time that can expire between power
transmissions from the controller necessitates large energy storage devices in all modules
Up until the present, the art has not included a system which modulates the pulse duration of both
polarities with data and allows power to be drawn from either polarity depending on the data
being transmitted. It is now possible using this system to power and communicate with hundreds
possibly thousands of modules on a low cost cable
Whilst the industry has been well served by standard communication techniques where power and
data are run in separate cables there has been a long felt want for a system which enables
communication and power transmission over long distances say greater than 5 kilometers and
particularly in environments where power voltage and current must be kept at low levels for
safety reasons but without compromise to data transmission time Such a system can be used to
advantage in explosive mining environments where long distances require increased power
transmission but regulation requires a power not to exceed a predetermined maximum and where
data transmission is desirable 100° c of the time
THE INVENTION
The present invention seeks to overcome theaforesaid prior art disadvantages by providing a two
wire communication system in which data and power are transferred over the same two wires
using a bi-polar signal such that useful data can be transmitted independant of and during power
transmission without loss of data transmission time
According to the invention 100% of the transmission time is used in data transmission without
affecting the transfer of power to the modules connected to the two wire conductor According tc
the prior art in comparison, up to 50% of transmission time may be lost in transfering power to
the modules
The arrangement of the present invention utilises a bi-polar signal which has a very large noise
margin As each period is followed by a period of the opposite polarity and only one value
(analogue or digital) is conveyed during each period, there is no fixed timing with respect to data
Also, the line speed can be increased or decreased at an arbitrary baud rate, because timing
information for data sampling is passed with each transition of the polarity Further, the
arrangement of the invention can support full duplex protocols on a single two wire conductor
system The protocol supports two data channel for simultaneous independent data transmission in
both directions.
It is one object of the invention to provide a two wire communication protocol for a
communication system which is capable of transmitting data in terms of pulse duration together
with power to at least one but preferably a multiplicity of modules connected to the two- wire
conductor wherein useful data may be sent 100% of the time and allow the designer to specifiy
the power duty cycle required for the application
In one broad form the present invention comprises
a two wire communication system capable of transmitting data and transferring power by
means of an electrical bi-polar waveform across a two wire conductor from a controller
in communication with said conductor to at least one module in communication with said
controller and/or data from said at least one module to said controller, the system including a
remote electrical device in communication with said controller,

wherein useable data may be continuously transmitted across said two wire conductor
independent of and during power transmission between said controller and said at least
one module without loss of data transmission time and without affecting the transfer of
power to said at least one module
In another broad form the present invention comprises
a two wire communication system capable of transmitting data and transferring power by
means of an electrical bi-polar waveform across a two wire conductor From a controller
in communication with said conductor to at least one module in communication with said
controller and/or data from said at least one module to said controller, the two wire system
including a remote electrical device in communication with said controller,
wherein useable data may be continuously transmitted across said two wire conductor
independant of and during power transmission between said controller and said at least
one module without loss of data transmission time and without affecting the transfer of
power to said at least one module; wherein the system is capable of using up to 100% of
available transmission time to transmit data without affecting transfer of power to said at
least one module, and wherein data and power transfer are effected through the same transmission
line
According to a preferred embodiment a plurality of modules are connected in parallel and which
are each capable of transmitting and receiving data across said conductor
Preferably, when the controller is transmitting data said modules are capable of drawing power
and when each said modules transmit data they do not draw power from said controller nor from
other modules
Each module is capable of transmitting data by putting a low impedance signal across said two

wire conductor wherein, said low impedance signal from said module for data transmission does
not distort pulse duration allowing said controller to transmit data on the two-wire transmission
line to any value independant of said impedance signal from each module
The low impedance signal may convey analogue or digital information by either
modulating the current, voltage or duration of said low impedance signal
In a further broad form the present invention comprises,
a two- wire communication system for transmitting power and data between a controller and at
least one module, said system including a two wire transmission line including two data channels
which allow two independant bi -directional communication channels between the controller and
said at least one module wherein power may be drawn by said at least one module whilst ever the
controller is transmitting data on either data channel, wherein when said module is transmitting
data back to the controller no power transfer is possible to other modules
In another broad form the present invention comprises a two wire communication system for
transmitting power and data between a controller and at least one module, said system including a
two wire transmission conductor including two data channels which allow two independant bi
directional communication channels between the controller and said at least one module wherein
power may be drawn by said at least one module whilst ever the controller is transmitting data on
either data channel, wherein when said module is transmitting data back to the controller no
power transfer is possible to other modules, wherein the system includes a P-side channel
allowing bi-directional data flow and power transfer from said controller to said at least one
module and an N- side channel allowing bi-directional data flow and power transfer between the
controller and said at least one module, wherein, when data is transmitted on said P- side
channel, said controller modulates at the P- side pulse width to effect data transfer such that

the system is capable of utilising up to 100% of the transmission time to transmit data without
affecting the transfer of power across said two wire transmission conductor
According to a preferred embodiment there is provided means at the controller and modules to
convey data to connect remote electrical devices and receive data from said connected remote
electrical devices According to the preferred embodiment there are a plurality of sparsely
separated modules connected in parallel across said conductor along with one controller which i:
connected in parallel across said two- wire conductor.
Preferably a bi-polar signalling scheme is used which provides high noise immunity The two
polarities of the two wire conductor are designated P -side and N-side, wherein, the pulse width
of the P-Side pulses and N-side pulses are modulated by the controller to convey all data to all
modules connected to the two-wire conductor
Preferably, all modules connected to the conductor can take power from the conductor
when the controller is transmitting data The relative duration of the controller data compared
with the module data determines the power duty cycle for the conductor
Preferably, the power available to the modules connected to the conductor can be traded off
against communication speed
Modules connected to the conductor can pass data to the controller by putting low impedance
across the conductor The controller can then modulate the duration pf the pulse in response to
the low impedance signal from the module
The low impedance signal from the module does not distort the duration of the pulse directly, so
the controller can still force data on the conductor ro any desired value independently of the
modules low impedance signal
Further, the module"s low impedance signal may convey analogue or digital information by

either modulating the current, voltage or duration of the low impedance signal.
Accordingly, the present invention provides a two wire communication system capable
of transmitting data and transferring power by means of an electrical bi-polar
waveform across a two wire conductor from a controller in communication with said
two-wire conductor to at least one module in communication with said controller and
capable of transmitting data from said at least one module to said controller; the
system comprising a remote electrical device in communication with said controller;
wherein the system is capable of continuous transmission of usable data across said
two wire conductor independent of and during power transmission between said
controller and said at least one module without loss of data transmission time and
without affecting the transfer of power to said at least one module.
The present invention also provides a two wire communication system capable of
transmitting data and transferring power by means of an electrical bi-polar waveform
across a two wire conductor from a controller in communication with said two-wire
conductor to at least one module in communication with said controller and capable of
transmitting data from said at least one module to said controller; and a remote
electrical device in communication with said controller; wherein useable data may be
continuously transmitted across said two wire conductor independent of and during
power transmission between said controller and said at least one module without loss
of data transmission time and without affecting the transfer of power to said at least
one module; wherein, said data is transmitted across said two wire conductor to said
modules by pulse duration signals at the same time power is transmitted to said
modules; wherein the system is capable of using up to 100% of transmission time to
transmit data without affecting transfer of power to said at least one module.
The present invention will now be described according to a preferred but non limiting
embodiment and with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 is a block diagram of an overview of the system according to one
embodiment of the invention.
Figure 2 is a block diagram of the controller according to one embodiment of the
invention.
Figure 3 is a block diagram of the module according to one embodiment of the
invention; and,
Figure 4 is a block diagram of a P-Side N- side line protocol according to a preferred
embodiment of the invention.
Figure 5 shows a schematic example of a system arrangement involving monitoring of
emergency stop switches; and
Figure 5a shows the arrangement of figure 5 with one emergency stop switch
operated.
DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION
The DLPCS according to the invention was developed for use in particular, though not
exclusively in long distance mining operations where explosive atmospheres require
that power voltages and current be kept to safe minimums.
Due to large power and data transmission distances in mining applications constraints
on transmission of power would normally compromise data transmission. These
constraints are not an issue in relatively short distance communications in normal
above ground operations presently satisfied by prior art technology.
A preferred embodiment of the invention is shown in Figure 1 and comprises a
schematic layout of the two wire communication system. The system shown
comprises a controller 1 including means to receive inputs 2 and deliver outputs 3 and
in communication with a first end 4 of a two ------------------------------------------------------
wire conductor 5 comprising an L+ wire and an L- wire The system further comprises a
multiplicity of modules 6, 7 and 8 each remote from one another and which are in communication^
with said L+ and L- wires such that each module is in communication with controller 1 and in
communication with each other module The system is such that data can be transmitted from the
controller 1 onto the transmission line L+and L- and received at said modules 6, 7 and 8
Data can also be transmitted from any one module 6, 7 and 8 onto the transmission lines L+ and
L- and received at the controller 1 and at any one of the remaining multiplicity of modules
By means of connection inputs and outputs 2 and 3, data is transferred between remote
electrical devices and the controller 1
Figure 2 shows a controller according to a preferred embodiment. The controller includes a
power supply 13 which converts high voltage power to low voltage power levels appropriate for
the chosen application Processor 14 is programmed to effect all the conrrol and timing functions
inside the controller Remote electrical devices are connected to the controller via Inputs and
Outputs 12 The bi-polar driver 1 1 is a controllable power source which can drive power into the
conductors L+ and L- in a negative polarity The current being drawn bv modules connected to
the two wire !ineL+ and L- is monitored by current measurement 10. The voltage on the line L+
and L- is measured by voltage measurement 9
Figure 3 shows a block diagram of the module according to one embodiment of the invention.
The module includes power supply voltage regulator 1 7, storage capacitor 20 and steering diode
2 1 The module"s reply circuitry comprises Level Shift 18, reply transistor 23 and steering diode
22 Data and timing is taken from receive clock 19 The processor 25 is programmed to effect all
the control and timing functions inside the module Remote electrical devices are connected to the
module via inputs and outputs 24

Figure 4 shows a block diagram of a P-Side N- side line protocol according to a preferred
embodiment of the invention
The P-side channel and the N- side communication channels are bi directional communication
channels between the controller and the modules 6, 7 and 8. When transmitting data on the P-
side channel the controller 1 modulates the P- side pulse width to effect data transfer According
to the preferred embodiment of the invention, three symbols are used to effect data transfer on
the P-side, namely a synchronous pulse 46, a zero pulse 44 and a one pulse 45 A reply pulse 48
has the same period as a one pulse 45 The period of the synchronous pulse 46 is longer than the
one pulse 45 The one pulse 45 is longer than the zero pulse 44
A synchronous pulse 46 alerts all modules connected to the line that new data follows The digital
data in the new data to be transmitted is represented by zero pulses 44 and one pulse 45
If the controller wants to transmit data on the P- side channel it transmits Zero pulses
44 and one pulses 45 according to the digital data being transmitted If a module is transmitting
data on the P- side channel the controller issues a zero pulse 44 and modulates rhe period to a
one pulse 45 if a low impedance is measured during the zero pulse 44 When a low impedance is
placed on the two wire conductor by a module the line voltage is reduced and line current is
increased as in the reply pulse 48
When transmitting data on the N- side channel the controller modulates the side pulse width to
effect data transfer According to the preferred embodiment of the invention , three symbols are
used to effect data transfer on the Signal side , a synchronous pulse 47, a zero pulse 41 and a one
pulse 42 A reply pulse 43 has the same period as a one pulse 42 The period of the synchronous
pulse 47 is longer than the one pulse 42 The one pulse 42 is longer than the zero pulse 41
The controller transmits a synchronous pulse 47 to alert all modules connected to the line that

new data follows The digital data to be transmitted is represented by zero pulses 41 and one
pulses 42 If the controller wants to transmit data on the N- side channel it transmits Zero pulses
41 and one pulses 42 according to the digital data being transmitted If a module is transmitting
data on the N- side channel the controller issues a zero pulse 41 and modulates the period to a
one pulse 42 if a low impedance is measured during the zero pulse 41 When a low impedance is
placed on the two wire conductor by a module the line voltage is reduced and line current is
increased as in the reply pulse 43 The controller reads the current measurement 12 and voltage "
measurement 11 to determine if a module is placing a low impedance on the conductor and
modulates the period to the same length of a one pulse 42 if a low impedance is detected If there
is no reply from a module connected to the conductor the controller terminates the pulse when it
is equal to a zero pulse 41
In the foregoing embodiment, digital data is transferred over the P- side channel and the signal N-
side channel. A higher level protocol enables addressing and arbitration between modules so
individual modules can be individually accessed However it is clear that many high level
protocols including full duplex communication can be supported using the two communication
channels on the P- side and N- side
It is also clear that the pulse period can be modulated with analogue data instead of the digital
modulation used in the foregoing embodiment In fact, any number of pulse symbols and analogue
modulation of the pulse period could be supported under a high level protocol
Refering to figure 5 there is shown an example of the use of a system in accordance with the
present invention The system shown is applicable to transmission of data relating to a conveyor
belt used for example in mining operations particularly though not exclusively where
communications over 5 kilometers is required and where the potentially explosive atmospheres

common in mining, limits the energy that may be applied to wire conductors to avoid ignition of
explosive gas The system includes a controller 50 linked to one end of a two wire
communication line 5 1 and at the other end, to an end of line module 52 The system further
comprises a plurality of additional modules 53, 54, 55, 56 and 57, connected in parallel and in
electrical communication with respective associated switches 58, 59, 60, 61 and 62
In accordance with the system set up, the emergency switches are monitored for correct
Operation and should any one of switches 58, 59, 60, 61 and 62 be operated the end of line
module 52 will be open circuit and will go off line in view of the series connection with module
52 Each emergency stop switch has two contacts which are operated simultaneously should the
emergency stop switch be operated The second of the two contacts is monitored by the modules
53, 54, 55, 56 and 57 allowing the modules to report back to the controller on which emergency
switch has been operated
Figure 5a shows the arrangement of figure 5 wherein emergency switch 60 has been operated.
Two wire communication line is now open at module 55 rendering modules 56 and 57 to be off
line Module 55 will send data backto controller 50 indicating that it"s emergency switch 60 has
been operated
While a preferred embodiment has been described , it is understood that numerous variations anc
modifications may occur to those skilled in the art without departing from the overall spirit and
scope of the invention
WE CLAIM :
1. A two wire communication system capable of transmitting data and transferring
power by means of an electrical bi-polar waveform across a two wire conductor from a
controller in communication with said two-wire conductor to at least one module in
communication with said controller and capable of transmitting data from said at least
one module to said controller;
the system comprising a remote electrical device in communication with said
controller; wherein the system is capable of continuous transmission of usable data
across said two wire conductor independent of and during power transmission
between said controller and said at least one module without loss of data transmission
time and without affecting the transfer of power to said at least one module.
2 A two wire communication system capable of transmitting data and transferring
power by means of an electrical bi-polar waveform across a two wire conductor from a
controller in communication with said two-wire conductor to at least one module in
communication with said controller and capable of transmitting data from said at least
one module to said controller;
and a remote electrical device in communication with said controller;
wherein useable data may be continuously transmitted across said two wire
conductor independent of and during power transmission between said controller and
said at least one module without loss of data transmission time and without affecting
the transfer of power to said at least one module; wherein, said data is transmitted
across said two wire conductor to said modules by pulse duration signals at the same
time power is transmitted to said modules; wherein the system is capable of using up
to 100% of transmission time to transmit data without affecting transfer of power to
said at least one module.
3. A two wire communication system as claimed in claim 1, wherein said data is
transmitted across said two wire conductor to said at least one modules by pulse
duration at the same time power is transmitted to said modules.

4. A two wire communication system as claimed in claim 2 or 3, wherein data and
power transfer are effected through the same transmission line.
5. A two wire communication system as claimed in claim 4, wherein a plurality of
modules are connected in parallel and which are each capable of transmitting and
receiving data across said conductor.
6. A two wire communication system as claimed in claim 5, wherein when the
controller is connected in parallel across the conductor.
7. A two wire communication system as claimed in claim 6, wherein said at least
one modules are capable of drawing power when the controller is transmitting data.
8. A two wire communication system as claimed in claim 7, wherein when each
said at least one modules transmit data they do not draw power from said controller
nor from other modules.
9. A two wire communication system as claimed in claim 8, wherein each module
is capable of transmitting data by putting a low impedance signal across said two wire
conductor.
10. A two wire communication system as claimed in claim 9, wherein said low
impedance signal from said at least one module for data transmission does not distort
pulse duration allowing said controller to transmit data on the two wire conductor to
any value independent of said impedance signal from each module.
11 A two wire communication system claim 10, wherein said low impedance signal
may convey analogue or digital information by either modulating the current, voltage
or duration of said low impedance signal.

12. A two wire communication system as claimed in claim 11, wherein the two wire
conductor have polarities designated as first and second channels the first of which is
a P-side channel allowing bi-directional data flow and power transfer and the second
of which is an N-side channel allowing bi-directional data flow and power transfer.
13. A two wire communication system as claimed in claim 12, wherein said first P-
side channel allows two way communication between said controller and said at least
one modules.
14. A two wire communication system as claimed in claim 13, wherein; said second
N-side channel allows two way communication between said controller and said at
least one modules.
15. A two wire communication system as claimed in claim 14, wherein pulse widths
of the P-side channel are modulated by the controller to convey all data to all modules
connected to the two way conductor.
16. A two wire communication system as claimed in claim 15, wherein the pulse
widths of the N-side channel are modulated by the controller to convey all data to all
modules connected to the two wire conductor.
17. A two wire communication system as claimed in claim 16, wherein data is
transferred between the controller and said plurality of modules by modulation of the
pulse width of the P-side and N-side pulses.
18. A two wire communication system as claimed in claim 17, wherein the P-side
channel is independent of the N- side communication channel.
19. A two wire communication system as claimed in claim 18, wherein data is
transmitted on the P-side channel by modulation of the P-side pulse width.

20. A two wire communication system as claimed in claim 19, wherein power may
be taken from the two wire conductor during either N-side or P-side polarities whilst
ever said controller transmits data.
21. A two wire communication system as claimed in claim 20, wherein there is
provided means at the controller to measure the voltage of the conductor and the
current into the conductor such that low impedance replies from modules are
detected.
22. A two wire communication system as claimed in claim 21, wherein there is
provided means at the controller to control the duration of the power source in either
polarity, wherein the duration of the power transmission is represented in an analogue
or digital value.
23. A two wire communication system as claimed in claim 22, wherein there is
provided at said module means to sense the polarity of the conductor and measure
the duration of transmission in either polarity.
24. A two wire communication system as claimed in claim 23, wherein there is
provided means at the module to receive power from the conductor.
25. A two wire communication system as claimed in claim 24, comprising means at
the controller and modules to convey data to and receive data from connected remote
electrical devices.
26. A two wire communication system as claimed in claim 25, wherein there is
provided means at said at least one modules to reply on said conductor by placing a
low impedance across said conductor; wherein, said controller can modulate duration
of pulse in response to said low impedance signal from said module.

27 A two wire communication system as claimed in claim 26, wherein the
controller has therewithin a power source which can be impressed on the conductor in
a positive or negative polarity.
28. A two wire communication system, substantially as herein described,
particularly with reference to and as illustrated in the accompanying drawings.
A two wire communication system capable of transmitting data and transferring
power by means of an electrical bi-polar waveform across a two wire conductor from a
controller (1) in communication with said two-wire conductor to at least one module (6,
7, 8) in communication with said controller and capable of transmitting data from said
at least one module to said controller (1); the system comprising a remote electrical
device in communication with said controller (1) ; characterized in that the system is
capable of continuous transmission of usable data across said two wire conductor
independent of and during power transmission between said controller (1) and said at
least one module (6, 7, 8) without loss of data transmission time and without affecting
the transfer of power to said at least one module (6, 7, 8).

Documents:

203-cal-1999-granted-abstract.pdf

203-cal-1999-granted-claims.pdf

203-cal-1999-granted-correspondence.pdf

203-cal-1999-granted-description (complete).pdf

203-cal-1999-granted-drawings.pdf

203-cal-1999-granted-examination report.pdf

203-cal-1999-granted-form 1.pdf

203-cal-1999-granted-form 2.pdf

203-cal-1999-granted-form 3.pdf

203-cal-1999-granted-form 5.pdf

203-cal-1999-granted-gpa.pdf

203-cal-1999-granted-letter patent.pdf

203-cal-1999-granted-reply to examination report.pdf

203-cal-1999-granted-specification.pdf

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Patent Number

214259

Indian Patent Application Number

203/CAL/1999

PG Journal Number

06/2008

Publication Date

08-Feb-2008

Grant Date

07-Feb-2008

Date of Filing

11-Mar-1999

Name of Patentee

AMPCONTROL PTY LTD.,

Applicant Address

A CORPORATION OF NEW SOUTH WALES, 250, MACQUARIE ROAD, WARNERS BAY, NEW SOUTH WALES 2282, AUSTRALIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	KEVIN WALKER	33, RAVENSFIELD ROAD, BISHOP'S BRIDGE 2326, NEW SOUTH WALES, AUSTRALIA.
2	MIKE RAMPLIN	57, CURTIN STREET EAST, MAITLAND 2323, NEW SOUTH WALES, AUSTRALIA.

PCT International Classification Number

H04M 11/04

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	PP2293	1998-03-11	Australia