Title of Invention

"A HOST DIGITAL TERMINAL"

Abstract

The present invention relates to a host digital terminal (HDT) (1) use in a fiber access system providing network side interface of the (Optical Access Network) OAN (2) and connected to one or more optical distribution networks (ODNs) (3) characterized in that:an ODN interface; (Optical Destribution Network) an exchange interface a TMN (4) interface; and(Time Management Network)a user interface;said HDT having 6 sub units V5 protection unit (VPU) (5), V5 line termination unit (VLT) (6), V5 signal processing unit (VSP) (7), cross connect and timing units (XTU) (8), TDM(9)/TDMA termination controller (TTC) (10) and operation administration and maintenance unit (OAM).

Full Text

The present invention relates to a host digital terminal (HDT), the main station for use in an optical network based system referred to as fiber access system. This novel main station for use in the fiber access system (FAS) is a host digital terminal (HDT). The host digital terminal of the present invention is designed to prevent any loss or damage to the system due to failure of any component of the fiber access system. The improved host digital terminal of the present invention not only provides indications of failure of a component, but the system as such is designed to prevent interruption of despite failure of a component. The host digital terminal (HDT) interfaces with one or more Optical distribution network (ODNs), and a number of optical network units (ONUs), typically located in a building or street locations. The fiber access system comprising host digital terminal as the main station forms subject matter of a copending patent application. The novel host digital terminal of the fiber access system of the present invention provides network side interface of the optical access network (OAN) and is connected to at least one optical distribution network (ODN). The HDT provides at least one optical interface towards the optical distribution network (ODN) and provides at least one network interface on the network side of the optical access network (OAN). The HDT can be co-located with in a local exchange or at a remote location. It comprises the means necessary for delivering different services to the required optical network units (ONUs). It multiplexes and cross connects the bearer channel and other information channels onto appropriate timing slots of transmit and receive paths. All maintenance and operation functions for the fiber access system are supported by host digital terminal (HDT) of the present invention. The main station, i.e., the host digital terminal of the fiber access system has a capacity of operating at least 4 ODNs, each ODN being preferably supported by a separate ODN interface. HDT-ODN interface is capable of supporting at least 32 ONUs. The host digital terminal also has a management interface which enables communication with the operations system. The fiber access system, comprising host digital terminal of the present invention as the main station, can be provided in various configurations, e.g., FTTC (fiber to the curb), FTTB (fiber to the building) and FTTO (fiber to the office) based on passive optical network (PON). Accordingly the present invention relates to a host digital terminal (HDT) for use in a fiber access system providing network side interface of the OAN and connected to one or more optical distribution networks (ODNs) having an ODN interface; an exchange interface; a TMN interface; and a user interface; said HDT having 6 sub units V5 protection unit (VPU), V5 line termination unit(VLT), V5 signal processing unit (VSP), cross connect and timing units (XTU), TDM/TDMA termination controller (TTC) and operation administration and maintenance unit (OAM). The present invention can be understood clearly and explicitly from the accompanying drawings which define the features of the invention. These drawings, however, do not restrict the broad scope of the invention. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1 defines the architecture of the fiber access system comprising host digital terminal of the present invention as the main station . Figure 2 shows direct interface with the access system of the present invention with exchange. Figure 3 shows FAS in SDH network. Figure 4 shows the functional block diagram of HDT of the present invention. Figure 5 shows block diagram V5 line Termination Unit Figure 6 shows block diagram of V5 signal processing. Figure 7 shows block diagram of cross connect. Figure 8 shows block diagram of timing unit. Figure 9 shows block diagram of TTC. Figure 10 shows block diagram of V5 protection unit. Figure 11 shows block diagram of OAM. Figure 1 as accompanied with the present invention defines an outline of the fiber access system and defines the basic architecture of the fiber access system. The Fiber Access system finds different uses and applications. Of the various uses and applications of the FAS of the present invention, two major applications are : 1. Direct interface with exchange: This is applicable when HDT and exchange are in the same building or very close to each other. Minimum 32 numbers of 2Mb interfaces exist between HDT and exchange. Figure 2 shows direct interface of the fiber access system of the present invention with exchange. 2. Interface via SDH ring: This application is most suitable when a large size exchange is deployed and is extended to FAS subscriber via SDH ring. The SDH/ADM ring network provides transparent transport of the HDTV through 2 Mb interface. Figure 3 clearly shows FAS in SDH network. The host digital terminal employs use of time division multiplex/time division multiple access (TDM/TDMA) transport protocol over an optical distribution network as the communication mechanism with in itself and optical network unit (ONU). The subscriber interfaces are provided at the ONU. The optical network units (ONUs) form subject matter of a copending Indian patent application. Services available to the subscriber are either POTs or ISDN-BA or ISDN-PRA. The TDM/TDMA protocol is well known in passive optical networks wherein it is employed to permit transactions between a single base station and a plurality of base stations. The novel host digital terminal of the fiber access system of the present invention provides network side interface of the optical access network and is connected to at least one ODN. There are different interfaces associated with the Host digital terminal which are ODN interface, exchange interface, TMN interface and user interface. Host digital terminal of the present invention operates at least four ODNs through the specified interfaces. On the optical distribution network side, one HDT interfaces with upto four passive optical networks (PONs) each containing upto 32 optical network units (ONUs) located near the customer premises. Each ODN interface uses separate fibers for upstream (ONU-HDT) and downstream (HDT-ONU) transport. The HDT provides at least one optical interface towards the optical distribution network and provides at least one network interface on the network side of the OAN. The HDT can be co-located with in a local exchange or at a remote location. It comprises the means necessary for delivering different services to the required ONUs. It multiplexes and cross connects the bearer channel and other information channels onto appropriate timing slots of transmit and receive paths. All maintenance and operation functions for the fiber access system are supported by host digital terminal (HDT). Figure 4 represents the functional block diagram of HDT. For effective functioning HDT has various subunits which are: • VPU V5 protection unit • VLT V5 line termination unit • VSP V5 signal processing unit • XTU Cross connect and timing units • TTC TDM/TDMA termination controller • OAM Operation Administration and Maintenance unit All sub units of the host digital terminal (HDT) have following features in common: • The front plate of each plug in unit includes on line and fail indicators to provide continuous status indication and immediate indication of a failed component. • Units protected by redundant units are designed such that failures do not interrupt service. • Plugging and unplugging HDT sub units from a line backplane does not affect services on other units. • HDT sub units are keyed to prevent insertion into the wrong slot. Therefore the host digital terminal (HDT) of the present invention is designed to prevent any loss or damage to the system due to failure of a component. Not only indications of failure of a component are given, but the system is designed to prevent interruption of system despite failure of a component. V5 LINE TERMINATION UNIT (VLT): VLT subunits provide physical interface between local exchange (LE) and HDT through VLT cards. Each VLT terminates 16 numbers of 2 Mbps (El) tributaries as per CCITT recommendations. The HDT houses at least 2 such cards in VLT unit that actively terminates 32-E1 tributaries thus providing 2:1 protection. It interfaces with V5 protection unit (VPU), XTUs and operation administration and maintenance (OAM) cards. This card performs El tributary termination and frame synchronization, byte multiplexing/de multiplexing, testing and monitoring, communication and clock selection function as well. The El tributary termination and frame synchronization function includes electrical termination of 16 incoming 2.048 Mbps HDB3 streams, converts them to NRZ (Non Return to Zero) data, performs frame synchronization and clock recovery and finally sends the NRZ data and clock to byte mux/demux block. In transmit direction NRZ (Non Return to Zero) data are converted to HDB3 format and sent over the lines with respect to frame synchronization and transmit block. Byte multiplexing/demultiplexing function includes byte multiplexing the 2.048 Mbps NRZ (Non Return to Zero) data received from the 16 tributary termination blocks to generate two 16.384 Mbps streams. Similarly two 16.384 Mbps data is de multiplexed to generate 16 numbers of 2.048 Mbps NRZ (Non Return to Zero) streams. Testing and monitoring function is performed by performing different loop backs and monitors for line faults, alarms, slips, error conditions and the like. It inserts AIM pattern. Further in the event of any fault arising this card generates an interrupt to VSP and sends an error message to OAM and therefore protection switching takes place. The VLT card has a duplicated shared communication link with the OAM card through which maintenance and performance related data is exchanged. The clock selection function includes selecting any one part of receive clock and frame synchronization signal out of the received 16 pair of signals and sends the signal to the XTU card. Line termination function in this card is realized using line transformers, line termination chips, framers and the like. Further, one line termination unit (VLTP) is kept as a stand by unit to switch over in case of failure of any of the VLT units. Figure 5 shows the block diagram of V5 line termination unit. V5 SIGNAL PROCESSING (VSP): VSP card is the central V5 protocol processor and message switch. This card interfaces with XTUs, OAM and TTCs. It again performs signal processing, communication, packet handling, message switching and cross connect block control function. Signal processing function includes performing signal processing for upto 32 V5.1 entities or 8 V5.2 entities. VSP receives messages from subscriber user ports and V5.1/V5.2 messages from exchange V5 protocol entities. It processes PSTN protocol, BCC protocol, protection protocol, control protocol, link control protocol and D channel frame relay (for ISDN). For carrying out communication, the card has a 64 Kbp/s HDLC link with the active XTU and a similar link with the OAM card. It communicates with the 4 active TTCs over a 2.048 Mb/s time shared HDLC link each with 512 Kb/s data rate. It has two 4.096 Mb/s links with the active XTUs that accommodates 96HDLC links (Max.) carrying V5.1/V 5.2 messages. It has an ACIA port for testing the card. It performs, packet handling function by performing layer 2 and layer 3 processing on 96 numbers of bi-directional 64 Kbp/s to/from XTU. It performs LAPD processing on four 512 Kbps HDLC link constituting the 2.048 Mb/s link with the TTCs. Message switching function is performed by routing the embedded operations control messages to the appropriate entities. It multiplexes the OAM messages that are to be relayed to the remote units on EOC link. It acts upon the OAM messages that are meant for itself.. VSP issues the cross connect configuration messages to the XTUs as per V5 protocol messages and switching requirement. The heart of VSP is a micro processor which performs the protocol processing meeting the real time requirements. The same processor also controls all other devices in the card. Figure 6 defines the block diagram of the V5 signal processing sub unit of HDT. Cross connect and Timing Unites (XTU): Cross connect and timing unit houses two sub blocks, i.e., a block each for cross connection and for timing. The cross connect block connects data stream between TDMA and V5 links (i.e., between TTC and VLT units). It is basically a time switch which supports 4K ports (64 KBPS) interfaces to TTC/ODN and Ik ports (64kpbs) V 5.1/V5.2 exchange interfaces. The main functions performed by this block are: • Receiving four incoming data streams at 16.384 Mbps from each TTC card and 4.096 Mbps links from VSP cards. • Transmission of V5 data (multiplexed) at 16.384 Mbps to VLT cards by multiplexing with concentration • Extraction of the signaling slots from the V5 data, concentrating them into a serial stream and sending them to the VSP card through 4.096 Mbps links. • Transmission of four 16.384 Mbps signals to each of the four TTC cards. • Processor HDLC link control with VSP to receive switch matrix control information. The cross connect function is performed using the specific required chip. There are 12 such chips used, 2 each for receive and transmit from five TTC cards and two for transmit and receive links with VSP cards. All the switches are controlled by a microprocessor which receives switch matrix control information from VSP through HDLC link. The master control lies at OAM controller for configuration through V5 signal processing function which issues real time requests for configuration changes. Figure 7 represents the block diagram of the cross connect. Timing unit performs the function of synchronous equipment timing source. This function consists of accepting timing reference information from line, tributary, external or internal clock sources and generating system clocks, derived frequencies and synchronization pulses. Its main functions includes receiving 2.048 Mhz clock from either external, internal 2.048 Mhz clock or tributary clocks received from either of the two VLT cards, to select one of the received clocks and synchronize the onboard phase locked loop (PLLs) to generate Tx side system clocks (155.52 and 16.384 Mhz) and its derived frequencies., to provide 155.52 Mhz differential ECL clocks to TTCs BDS unit, to provide 2.048 Mhz, 19.44 Mhz, 16.384 Mhz TTL clocks to TTCs and XTUs and to provide IKhz, 8 Khz synchronization pulses to TTCs BDS unit. Figure 8 represents the block diagram of timing unit. The master phase locked loop accepts scaled down version of the selected reference clock from the VLT cards at 64 Khz. The master PLL is an all digital PLL fully implemented in a PLD. It generates reference clocks at 1.152 Mhz and 64 khz for the slave PLLs which are locked to the incoming reference. There are two slave PLLs of frequency 155.52 Mhz and 16.384 Mhz. TDM/TDMA Termination Controller (TTC): The TTC has interface with ODN, for optical signal and other side with XTU for payload and timing and with VSP for EOC messages. On the receive data TTC performs O/E conversion, clock extraction, data retiming serial/parallel conversion, frame word detection, descrambling, de encryption and formatting of data into four 16.384 Mbps serial stream to XTU. In the transmit path TTC performs serial/parallel conversion of 16.384 Mbps streams, encryption, overhead insertion, scrambling and finally E/O conversion to transmit data as optical signal at 155Mbps. EOC from the various ONU is extracted and after layer 2 function it is transferred to VSP on a shared link. This card has interface with OAM for operation and management and one link is provided for testing purpose. Ringing algorithm runs on this card during initialization of ONU which calculates ranging delay. This card provides interface for future broadcast and video unit (BVU). Data from BVU is transmitted with other data. One communication link (HDLC) has been provided with BVU. Three loopbacks and two JTAG scan chains are there to test various blocks of the card. On the card O/E & E/O conversion is done by receiver and transmitter modules. On the received path serial to bit parallel conversion and frame sync detection is done by SYN-155. Descrambling and decryption of the received burst is done by HTPC (HDT TDM.TDMA protocol controller) and data is stored in a DPRAM and from there to four FIFOS. From FIFO's data is transmitted to XTU at 16.384 serial stream. On the transmit path data from XTU and ECU are stored into 5 FIFO's. EOC ranging data and BVU control data are inserted into transmit stream as overhead PMC 5343. All control signals for FIFO read write as generated by HTPC. For all synchronization purposes this card receives various clock from XTU. Scanbridge, scan buffers and registers provide JTAG testability on the card. Figure 9 represents the block diagram of the TTC. V5 Protection unit (VPU): VPU identifies the faulty VLT, if any and switches the 2.048 Mb/s El tributaries to the HDT standby protection VLT unit. 2 Mbps (El) tributaries from the termination panel are connected to this card. Normally they are routed to the VLT1 and VLT2. In case of a failure the corresponding signals are switched to VLTP. The VLTs In case of a failure the corresponding signals are switched to VLTP. The VLTs sends an interrupt to this card in case of card failure and an error message to OAM. The control signals that helps to Mux/Dmux the 16.384 Mbps, tributary reference clock, drams sync and the like from 2 out of 3 VLTs are generated in this card. It performs self test and monitoring and sends and receives maintenance information through the shared ACIA link to/from OAM. Figure 10 defines the block diagram of V5 protection unit OPERATION ADMINISTRATION AND MAINTENANCE UNIT (OAM): OAM performs all operation and maintenance functions of the entire fiber access system Interfacing subsystems to OAM are VSP, XTU, TTC, VLT and VPU card, the OCC at ONU through message link and through it RTC, control terminal (CT) and user terminal (UT) through a F-interface. The cards functions can be characterized as operation, administration and maintenance function and also communication function. Under the operation, administration and maintenance function all the main maintenance function and test functions, configuration control, provisioning and the like. It collects and analyses the performance related data and passes them to CT. It configures the FAS network as per user commands issued from CT or UT. Under the communication function it is a 64 kbps HDLC link to both copy 0 and copy 1 of VSP. It provides a shared ACIA communication link to all other cards viz., TTC, XTU, VLT and VPU. Apart from this provides a Qx interface and a ethernet LAN interface. Figure 11 represents the block diagram of OAM. The backplane of the host digital terminal has a 8 layer PCB. Simulation of all critical signals is done before finalising the mother board design. While routing all results obtained during the simulation are incorporated. There are generally seven type of PCBs in the host digital terminal including motherboard which are VPU, VLT, VSP, XTU, TTC and OAM. Further, in host digital terminal, each critical units have been provided with 1+1 protection to achieve a better reliability. Each sub unit is also provided with additional protection. The host digital terminal has four subsystems which are administration, maintenance, transport and V5 signal processing functions. The administration sub module provides functionality's of provisioning which provides capabilities to provision and bring into service, an ONU. This involves ranging control and TDMA burst plan download. Further configuration management is maintained where the operator can change system configuration, i.e., number of HDT's and ONU's connected. Administration of customer configurations attributes as port allocated type of services used is also done. Depending on configuration data the overall TDM/TDMA burst plan is prepared. After initialisation control terminal downloads code to all functional blocks through OAM controller in HDT. Inventory management includes information of all service, system and performance entities are stored as objects. Maintenance function includes initialisation, fault location, recovery, testing and diagnostics and performance monitoring. Initialisation starts with power on self check of all the modules, minimum configuration set up, initial communication establishment between various modules and boot up of the whole system. The fault location and isolation involves analysis of hardware and software fault triggers leading to the location of fault. Fault location involves restricting propagation of fault within component/modules. The recovery involves the switch over, rerouting in case of malfunctioning data signal or control paths and software recoveries/rollback in case of software fault triggers. The system performs on-line diagnostics and testing of various modules and cards for preventive maintenance. It allows on demand testing and diagnostics carried out by the operator. The maintenance sub-systems gets the initialisation sequences from the user terminal. The initialisation procedures are invoked by the maintenance subsystem in the user terminal or by the operator commands. The testing and diagnostic results are forwarded to the control terminal in the network manager in the form of reports through the Qx interface. All remote commands for the optical network units are directly forwarded to the packet handler in the TDM block for sending over the operations link. Various alarms emanating from different Lcs/processes classified by an alarm handler and are forwarded to the control terminal. Performance monitoring covers collection, retrieval and storage of the data transport network performance data relating to digital facility performance and subsystem performance. The packet handler in the TDM block forwards the ONU performance data packets to the performance monitoring subsystems in the OAM. The performance messages from the local controllers are directly sent to the OAM. In the OAM the performance data is consolidated reformatted and dumped on the CT. The performance data dumping schedule are controlled by the operator or network manager. Further the transport subsystem is localized mostly to the TCC. It performs the functions related to ranging, configuration and security. Ranging includes ranging control of different ONUs. Configuration function includes the encryption/decryption between the HDT and the ONUs. Security function includes key generation and key synchronization between HDT and ONUs. Monitoring includes monitoring and reporting of performance data to maintenance module. V5 signal processing functions is a dynamic concentrator interface which provides transport for bearer channels and V5 signalling messages. The message flow between HDT V5 and LE V5 consists of five types of logical message links between HDT and LE. All these links are facilitated via a data link based on the LAPD. Layer two peer to peer messages are exchanged at the time of system initialization between LAPD processes at the two ends and multiple data links are established. There are separate data links for each protocol. The link control messages are between the link manager and the data link layer at the two sides that is HDT and LE. All control messages are multiplexed at layer 3 and carried over the control layer 2 data link over V5.1 interface. There are four type of messages flowing between AN protocol and LE control protocol in either direction over a control data link. They are port control messages, port control ack, common control and common control ack. The port control type of messages flow between individual port related control entities on either side by means of layer 3 address. The common control message is exchanged between two common control entities on either side of the V5.1 interface. The PSTN signalling messages from the ONUs are demultiplexed at the TDMA card in the HDT and sent to PSTN protocol in V5 processing block. The PSTN messages are exchanged between the HDT and the LE-PSTN protocols over one data link per V5.1 interface. The protocol is disconnected by disconnect request message. The ISDN D-channel data packets are multiplexed through a from envelope function in the V5 and are sent over a data link to the ISDN-D channel handling block in the LE. Further the bearer control message link applies only to V5.2 while protection protocol messages are as per V5.2. Messages between subsystems of HDT are mainly related to administration and transport; administration and maintenance module; administration and signalling module and signalling and maintenance module. The type of messages exchanged between administration and transport modules cane generally be categorized as • Messages related to bringing in/out of service various ONUs such as command to start ranging of specific or all ONUs. • Message for enabling/disabling encryption keys for individual ONUs. • Transport path performance reports such as accumulated BER counts. Administration and maintenance module covers messages of the type of reconfiguration reports in case it is done autonomously by the maintenance module and messages containing performance and alarm report for logging. Administration and signalling module includes messages for providing provisioning variants, V5 link Ids and interface Ids and PSTN and ISDN port control messages and signalling and maintenance module port blocking/unblocking messages for urgent and no urgent port maintenance, link blocking and unblocking messages and blocking/unblocking messages in case of protection switch over. The invention hereby has been described in brief and is a mere statement of invention, which does not and shall not restrict the broad scope of the invention. We claim: 1. A host digital terminal (HDT) (1) use in a fiber access system providing network side interface of the (Optical Access Network) OAN (2) and connected to one or more optical distribution networks (ODNs) (3) characterized in that: an ODN interface; (Optical Destribution Network) an exchange interface; a TMN (4) interface; and(Time Management Network) a user interface; said HDT having 6 sub units V5 protection unit (VPU) (5), V5 line termination unit (VLT) (6). V5 signal processing unit (VSP) (7). cross connect and timing units (XTU) (8), TDM(9)/TDMA termination controller (TTC) (10) and operation administration and maintenance unit (OAM). 2. A HDT as claimed in claim 1, wherein the said sub-units of the HDT are provided with on line and fail indicators at the front plate of each plug in unit in order to provide continuous status indication and immediate indication of a failed component. 3. A HDT as claimed in claim 1, wherein the said ODN interfaces with upto four passive optical networks (PONs) (11) each containing upto 32 optical network units (ONUs)(12). 4. A HDT as claimed in claim 1, wherein the said TMN interface accesses FAS through CT (13) and sends or receives common management information service element (CMISE) (14) messages to/from network manager and translates them to appropriate OAM commands. 5. A HDT as claimed in claim 1, wherein the said user interface is a proprietary interface provided at the end of the subscriber. 6. A HDT as claimed in claim 1, wherein the said sub units of the HDT are designed such that failures do not interrupt service. 7. A HDT as claimed in claim 1. wherein the said sub units are keyed to prevent insertion in the wrong slots. 8. A HDT as claimed in claim 1, wherein the said VLT (15) sub-unit of the HDl" provides interface between the local exchange and the HDT and provides electrical termination of incoming streams, converts them to NRZ (16) data, performs frame synchronization and clock recovery and sends the NRZ data and clock to byte multiplexer/demultiplexer block. 9. A HDT as claimed in claim 1. wherein the said VLT is adapted to perform and monitoring, communication function and clock selection function followed by sending the signal to XTU sub-unit. 10. A HDT as claimed in claim 1, wherein the said VSP is the central V5 protocol processor and message switch interfacing with XTUs. OAM and TTCs used for signal processing, communication, packet handling, message switching and cross block control function. 11. A HDT as claimed in claim 1, wherein the said VSP receiving message from subscriber ports and messages from exchange V5 protocol entities processing PSTN (17) protocol, BCC (18) protocol, protection protocol, control protocol, link control protocol and D channel frame relay. 12. A HDT as claimed in claim 1, wherein the said VSP communicates with active TTCs over a time shared HDLC (19). 13. A HDT as claimed in claim 1, wherein the said VSP issues the cross connect configuration messages to the XTUs as per V5 protocol messages and switching requirement. 14. A HDT as claimed in claim 1. wherein the said XTU is provided with two units which are cross connect block and timing unit. 15. A HDT as claimed in claim 14. wherein the said cross connect block connects data streams between TDMA (20) and V5 links. 16. A HDT as claimed in claim 14. wherein the said cross connect block receives incoming data streams from TTC card and VSP cards, extracts the signaling slots from the V5 data, converts them into a serial stream and sends them to the VSP card; followed by transmitting the generated signals to the TTC cards and process a HDLC link control with VSP to receive switch matrix control information. 17. A HDT as claimed in claim 14. wherein the said timing unit acts as the synchronous equipment timing source accepting timing reference information line, tributary, external or internal clock sources and generating system clocks, derived frequencies and synchronization functions. 18. A HDT as claimed in claim 1, wherein the said TTC has interface with ODN for optical signal and other side with XTU for payload and timing with VSP for EOC (21) messages. 19. A HDT as claimed in claim 1, wherein the said VPU(23) identifies the faulty VLT (22), if any and switches the tributaries to hot standby protection VLT unit. 20. A HDT as claimed in claim 1, wherein the said OAM unit interfaces with VSP. XTU, TTC, VLT and VPU card. 21. A host digital terminal for use in a fiber access system providing network side interface of the OAN and connected to one or more optical distribution networks (ODNs) substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

320-del-1999-abstract.pdf

320-DEL-1999-Claims.pdf

320-del-1999-complete specification (granted).pdf

320-del-1999-correspondence-others.pdf

320-del-1999-correspondence-po.pdf

320-del-1999-description (complete).pdf

320-del-1999-drawings.pdf

320-del-1999-form-1.pdf

320-del-1999-form-19.pdf

320-DEL-1999-Form-2.pdf

320-del-1999-form-4.pdf

320-del-1999-form-5.pdf

320-del-1999-gpa.pdf