Presently all the C-DOT exchanges have been upgraded to one of the following software versions available for different applications.

This is PSTN release to support normal subscriber features in different configuration of exchanges as SBM-RAX, MAX-L, ILT, RSU and TAX.

This release was being used by BSNL at sites, where main C-DOT exchange was having connectivity with private operator network. This release supported following features in addition to all the features of S/W 1_4_5.43_3 :

This release was being used by BSNL at sites, where CCS7 signalling and Network

Synchronisation was required. All the 'MAX-XL' exchanges were being

commissioned with this software. These two features were in addition to all the

features contained in S/W 1_4_5.43_3.

This software release 2_1_1_1 was introduced to offer new features such as ISDN, 800K BHCA etc. as well as merge all the features of the earlier three different software releases. Thus all the features could be offered to subscribers at any site after retrofitting S/W release 2_1_1_1. The last patch in this series was 2_1_7.9_1.

The software release 2_2_1_4 was introduced to support V5.2 protocol capability in addition to all the features supported by S/W 2_1_1_1. This provided connectivity with WLL (Access Network) of HFCL/Hundai, LG or Lucent technologies & ANRAX  of C-DOT technology. This software supported subscriber category based charging. Moreover same S/W supported Intelligent Network services also. The last patch in this series is 2_2_4.4_4 for PSTN and 2_2_5.5_4 for IN working.

New S/W release 2_2_1_6 has been introduced to provide dynamic control for 94/95/98, default Detail Bill on 94/95/98 routs, Line Monitoring Feature, Increase in 'AI' links to '14' in MBM & '11' in SBM. These facilities are in addition to all the features supported in S/W 2_2_1_4. Detail of all the features is given below:

It will be possible to connect '14' interfaces on V5.2 in one BM with single PCM Connectivity. This will find use for 'AN-RAX' connectivity.

Dynamic locking/unlocking is available for 9X (except 90 and 96) levels as 'OG-UPTO-REG' access. Dynamic Locking/unlocking of Levels 92,93,94, 95, 98,99  is achieved by Dialling 124 ABCD1 and 124 ABCD5 respectively. This procedure will lock/unlock 9X Level. Individual locking of 94, 95 & 98 is not supported. CDRs will be generated for 9X except 90 and 96  calls by default, in addition to '0' & '00' levels. Meter increment for 9X level calls will be done in 'STD' counters instead of Local Counters. Detail bill for these calls can not be stopped by any means.

For various features invocations like Dynamic locking/unlocking, now 'announcements will be fed instead of tones. The announcements are following:

1. This feature has been invoked successfully.

2. Feature invocation has failed

In case of Call-waiting, Calling party will get Queue Announcement instead of RBT Announcement in this case will be "kindly wait, you are in Queue".

For this, there should be no data (subs/trunks) equipped in the BM. All the frames should be unequipped. Unequip all 'mfc' cards also.

It is possible to assign separate STD code for RSU/Access Networks belonging to different SDCA's. For this, 'Area Code' field is available in 'MOD-XCOD'  command. If Area Code field is not defined in an 'XCOD', then system parameters ARCD* will be referred for prefixing Area Code to CLI for that 'XCOD. Area Code Defined in 'MOD-RBM-XCOD' will superseed, the code defined either in 'MOD-XCOD' or 'ARCD*' parameters.

By using 'MOD-RBMNRM-CONFIG' command special services like 131, 198 etc. can be mapped separately for RBMs. For this special service code 131/198 etc. should be opened on 'Alternate Nos' of the Main Exchange. If these routs are opened as normal rout, then mapping will not be possible. For Access Network, command 'CRE-ANNRM-CONFIG' can be used to map special service codes to DIR. NOS. belonging to respective 'AI' Nos.

New Codes have been covered in para 1.2.2.3.

This command has been enhanced to get list of subscribers having different 'SUB-CAT'.

Transactions on IOP upto '10000' records will be preserved in Trans files, after which, records will be overwitten. The file size has been reduced to half as compared to previous release 2_2_1_4. Trans files now will be transferred during IOP synchronization.

. Otherwise call will fail for categories for which such 'CRG-RTN' are allotted. In addition some recovery messages will be generated which may cause frequent system initialization.

Caution : In this case, ISD calls, to some countries specially 'Gulf Area' may fail.

B. MOR-R2 Signalling                                  

Always define, Ist digit of Area Code as '0' in system parameters i.e. ARCD-DGT1=10. Also define NUM-ANI=10 in order to ask for 10 digits CLI.

As per New 'TEC' requirements, a route 1951/1952 is to be opened towards IVRS. Now, when a call for deleted subscriber is received, the exchange will route the call towards IVRS with digits '195x' prefixed to the Dialled digits. As a result, the deleted No. shall be sent to IVRS, which will directly announce the Changed Number to the Calling Party. To achieve this, following steps of Data creation are required :-

1. 'MOD-SYS-DIRNO'

OPR-TYP : CRE

TYPE : IVRS

DIRNO : 1951 or 1952

2. 'CRE-ROUT'

ROUT-CODE : 1951, DIGIT-LENGTH = OPEN

with O/G TGP opened towards IVRS. This 'TGP' should have "Rank of

digit = 5".

3. Delete the DIRNOs

DEL-SUB

DIRNO : No. to be Deleted

TEN : < >

MODE : IVRS

BSNL Subscribers availing Answering Machine Service (AMS) can divert their calls on Level 170511, 170512, 170513 etc. or any other 1x level as desired (except 10x).

Crp command 'DISPL-SW-CONFIG' has been modified to show complete Software Release Identification on its first page of the output.

CCS7 Message Analyser is available in S/W 2_2_5.4_6 ownward; similar to MF Signalling Analyser. This will monitor the messages between two exchanges when calls are made on #7 trunks. The analyser will display the sequence of forward and backward message transmitted between two exchanges as per call basis on the #7 trunks put on 'ISUP' observation using 'MOD-TRK-OBS' command. Reports can be seen by crp command 'DISPL-NSMA-RPT'.

Local PCOs can be given access level as 'OG-UPTO-REG' now, thus allowing them to have access to '95' level routes. In this case, charging for local call will be done as per 'CRG-RTN' defined in 'SYS-PARAM' - 'PCO-MTR-LCL'. For route calls, charging will be done as per 'CRG-RTN' defined in route parameters.

The ISDN switching functionality is offered for both types of customer interfaces viz Basic Rate Access (BRA) and Primary Rate Access (PRA). A new type of terminal unit, ISDN Terminal Unit (ISTU) has been introduced. The new cards supported in this frame are ICC (ISDN Concentrator Card), ITC (ISDN Terminal Controller), BRL (Basic Rate Line Card) and PRL (Primary Rate Line Card). In the basic call processing, the following interworking scenarios are supported:

The CDOT DSS Operating System (CDOS) currently being used in the main processor complexes of the switch, is suitably modified to support the new hardware involving 68040 and 68302. With the induction of HPC in place of BPC in APU (AM), SCU (CM), BPU (BM), SUM (#7SU) and HMS in place of MSC & MSD in all the BMs of MAX-XL, the combined processing power is fully exploited to enhance the load handling capability of CDOT-DSS beyond 800 K BHCA. With the induction of HPC as CPU in SUM (#7SU), the message handling capacity is increased upto 2000 messages/sec as against 625 messages/sec with BPC as CPU. Also, it supports up to 64 channels as against 32 with BPC as #7SU CPU, thereby doubling the availability of CCS7 links for connectivity.

1.             CLIP                     NO                     NO

2.              CLIR                    NO                     NO

3.               CLIRO                NO                     NO

4.               MCID           See Note-1              NO

5.               MSN                   NO                      NO                        Only for ISDN

6.                DDI                     NO                     NO                        Only for ISDN

7.               SUB                     NO                    NO                          Only for ISDN

8.              COLP                   NO                      NO                         Only for ISDN

9.              COLR                    NO                    NO                         Only for ISDN

10.             COLRO                NO                    NO                         Only for ISDN

1.                    LH                             NO                       NO

2.               CFU (fixed)                *224#                     #225#            See Note-2

3.               CFU (SEL)                *14 B#                     #15#              See Note-3

4.               CFB (GRP)                  NO                        NO                See Note-2

5.               CFB (SEL)                *220 B#                  #221#             See Note-3

6.                CFNR (GRP)            *228#                    *229#              See Note-2

1.                 CW                        *18#                          #19#                  See Note-4

2.                 CH-WOR       HOLD/RETRIEVE            NO                   Only for ISDN

3.                 CH-WR           HOLD/RETRIEVE           NO                   Only for ISDN

4.                 TP                  SUSPEND/RESUME         NO                   Only for ISDN

5.         Hot Line (Timed)  *20 B#                               #21#                  See Note-3

6        . Hot-Line (Un-timed)      NO                             NO

1.                  CNF-3PTY                     HSF *490 B # to add B       Only for PSTN

                                                              HSF *493 # to toggle

                                                             HSF *494 B # to drop B

                                                             HSF *494 # to drop last

                                                             HSF *492 # to activate

2.               CNF-6PTY                     As above with difference that dial 491 in place of 490 to add a party B.  .                                                       Before adding any new party, *492 # should be used. Only for PSTN

1.               Dynamic Locking     To Select the password  *23 ABCD ABCD #          

                                                      To change the password: *23 ABCD PQRS #      

                                                       To select current access: *24 ABCD N #  where N is the current access Level        N=0 for all allowed,  N=1 for O/G upto Local,  N=3 for O/G upto STD,N=4 for O/G upto 10X,     N=5 for O/G upto 98/94/95/92/93 level (in 7.5 patch)

 2.               Alarm (Once)                 * 16 hh mm #            #17 hh mm #            See Note-6

3.                Alarm (DLY)                   *226 hh mm #             #227 hh mm#           See Note-6

4.                 Queuing                         *686#                           #685#                      Only for PSTN See Note-7

5.             Directed (DBE) call           *681 TEN # for line

                                                            *682 TEN B# for trunk

                                                            *683 TEN # for Tone/Annc.

6.             AOC-E & AOC-D               NO                           NO                           Only for ISDN

7.         16 Khz for Home Meters      NO                            NO                          Only for PSTN See Note-8

8.            Distinctive Ringing            No                             No                          Only for PSTN subscribers

ABSENTEE_FIXED_NUM_ACT                        28                                            498

ABSENTEE_FIXED_NUM_DEACT                  29                                             499

3W_CONF                                                             250                                            490

6W_CONF                                                             251                                            491

ADD_CONF                                                          252                                            492

CONF_TOGGLE                                                   253                                            493

DROP_SEL_PARTY                                            254                                           494

Note - 2 : These features are not part of TEC/DOT specification/requirement but very useful for the users. The  feature permits the subscriber to divert the call to a group of pre defined numbers with flexibility to activate/deactivate the feature by the subscriber.

Note - 3 : The diversion no. B can be local, regional, STD or ISD and diversion will be activated based on the current dynamic access  level of the subscriber. However, when the call is being diverted, the subscribed access barring is checked.

Note-4 : Invocation procedure for ISDN and PSTN subscribers are different. A ISDN subscriber uses functional keys to put the existing call on hold to receive another call in waiting. The PSTN subscriber has to invoke the feature by HSF and can toggle between two subscribers by using HSF repeatedly. Alternatively the call in waiting can be accepted by ISDN as well as PSTN subscribers by releasing/clearing the current conversation.

Note-5 : Invocation of six party conference is subject to the condition that CNF card is equipped in the BM in which subscriber is connected.

Note-6 : All the alarm requests can be cancelled by using the procedure #17#. Also, it is possible to request the operator to book the alarm call for the subscriber subject to the limitation that a maximum number of six alarms can be booked on a subscriber interface.

Note-7 : The facility is valid for ISDN interface when configured as Hunt Group. However an individual ISDN subscriber can subscribe to CW facility so that more than one calls can wait on an ISDN interface as specified/allowed by the administrator for that interface.

Note-8 : 25% of the total termination capacity can be used as 16 KHz ports subject to the equipage of compatible hardware.

The new telecom policy enables private operators to offer basic and cellular telephony services in different telecom circles. The different operator exchanges will be connected amongst themselves and to the DOT controlled TAXs by trunks. There is a need that the various telecom service providers keep track of the revenues which are shared by them, on the basis of resource utilisation. With revenue metering on trunks implementation in C-DOT DSS, it can be configured as TAX with function as network's hand-over point. Online charging on per call basis is done on Trunk Groups (TGPs). At the end of every successful call, the charge meter of TGP is incremented by the applicable charge depending on the distance, type of day and call duration. Also information of number of successful calls on the TGP is maintained. A detailed billing record for every successful call can also be generated if required A trunk group can be put under detail billing observation in each configuration of C-DOT DSS as Local/Tandem/TAX or ILT. However calling party identity will be part of detail billing records i.e. CAMA functions, only when exchange is configured as TAX or ILT. In case of revenue metering on ISUP trunks, the meter counters are incremented and detail bill records are made by incrementing the counters for actual charge units in both the cases of CHU and CHB. All the trunk groups are associated with Local, STD and ISD meter counters. In case of Bothway trunk groups, two sets of counters (one each for I/C and O/G) are associated with each TGP.

Different commands have been modified to support 4 digit year field to solve the problem of year 2000.

As per definition/specification in the latest revised specifications of TEC, the concept of Killer Trunks has been implemented. The scope of definition has been improved by C-DOT to ensure unmanned operation of interconnecting resources and their maximum availability to carry the traffic. This feature will block the faulty junctions automatically and restore after monitoring the fault removal. This will be very useful feature at ILT and TAX, connecting the remote exchanges with limited resources.

As per definition of charging, in addition to distance and day type, the time is also a important factor to decide the charging. Accordingly, a day i.e. 24 hours are divided in different time zones. If a call progresses to the next tariff zone, the corresponding tariff class becomes effective for subsequent period.

As per decision of ITU-T, the international numbering plan has been increased to 17 digits from 16 digits. To take care of future requirement, the routing capability has been increased to 20 digits.

To meet the requirement of automatic reporting of large duration calls, it is possible to define the threshold for "Call Duration" as well as "Charge Units".  An exception report is generated for all the calls, crossing the threshold value. The exception report is generated on the OOD as well as printer. It is possible to retrieve the records at any time as these are also available in the disks as logs. The report include all the details, related to the call and required by the administrator, e.g. Calling Party Number, Called Party Number, Call Duration, Charge Units, Time of Originations etc.

Keeping in view the topology of telephony networks in the SSAs, the trunk interface (Analog or Digital) has been implemented in RSU. It is possible to parent the smaller exchanges at RSU itself. (Fig. 3.1) This results is advantages as listed below:

i) Avoid the requirement of separate media/connectivity for smaller exchanges upto main exchange.

ii) Efficient utilization of media, between RSU and Main Exchange by sharing the resources to carry the traffic to/from the network to smaller exchanges.

iii) In case of media failure between RSU and Main Exchange, Connectivity to Smaller Exchanges is maintained with RSU which may be installed at Block/Taluka level.

With implementation of CAMA along with suitable MMI commands to generate the detail bill from SSA HQ for smaller exchanges/parented on R2 signalling, it is felt that C-DOT DSS is ideally suited for Indian Telecom Network, specifically for SSA Networks.

The existing command has been enhanced to support the following functions: Display of billing records of Subscriber and Trunks, Display of billing records of subscriber, belonging to specific level e.g. in the numbering plan 548xxxx, it is possible display the records of 100 subscribers belonging to 54823xx. Display of TGP/Subscriber bill records with exceptionally higher charge units. Display of CAMA records in the format of detail bill to facilitate the Administrator to generate the detail bills for smaller exchanges from a centralised place.

It is possible to get the total number of charge units to monitor the revenue generation in the exchange. The flexible implementation of the command facilitate the Administrator to monitor the revenue generation for different application as Local, ILT or TAX. In case of an ILT exchange, it is possible to get the revenue figures with break up for the subscribers of its own exchange as well as revenues for parented exchanges, for which it is functioning as TAX.

It is used to notify the caller that the incoming call is from distant place. The subscriber gets one type of ringing for Local calls and a different type of ringing for STD/ISD calls. The implementation of this feature is dependent on the type of Power Supply used in the exchange. In case of already commissioned sites, this feature will be available to the subscribers only after implementing the necessary modifications as the Power Supply Card and compatible TIC PROMs. No special procedure is required for activation, deactivation or usage of the failure and it is available by default to all the subscribers in the exchange.

Due to integration of multiple technologies in the network along with coexistence of different interworking scenarios, the inbuilt signalling tracer is required to collect the details of call failures and take the corrective measures. The Multi Frequency Signalling Analysis is possible in C-DOT DSS on one or more than one trunk, simultaneously but a max. of 32 trunks at a time. The details of forward and backward signal are logged in IOP which can be displayed any time.

In case of partial failure i.e one or more PCMs have failed, audio and visual alarm is raised for the attention of O&M personnel to take corrective measures. The exchange administrator can programme the parameters to control the raising and retiring of alarms.

To meet the requirement of new tariff plan, the tariff classes have been increased to 16.

Signalling System #7 (SS7) is a common channel inter-exchange signalling mechanism that is intelligent, efficient, flexible and economical. The network comprising of switches with SS7 capability also provides the infrastructure for network features and services such as ISDN, Intelligent Network, Mobile Applications, Operation and Maintenance Applications, etc.  The system has a 4-layer architecture. Layer1 provides the Physical Layer, usually a 64 Kbps channel in a digital environment using PCM technique for transmission. Layer2 provides the Datalink Layer functionality and is responsible for reliable transmission of messages over a link without loss, duplication or mis-sequencing, through flow control and error correction mechanisms. Layer3 provide the Message Handling (discrimination and routing) and Network Management (Traffic, Link and Route Management) functionality a part of the Network layer. All these comprise the Message Transfer Part (MTP). Level4 is for the User Parts. ISDN User Part (ISUP) is one that defines the logical sequence of events for a particular application using the services of the lower layers. ISUP defines the procedure for control of switched services in ISDN and covers both voice and non-voice (circuitswitched data) applications.

The Network Synchronisation Controller (NSC) card in MAX-XL system is capable of synchronising its own clock to the network clock and supplying it to the exchange. This network clock is available through the DTKs coming from either a higher level or a peer level exchange and is extracted by the DTS card in a Digital Trunk BM before being given as input to the NSC cards in the CM complex. With this synchronisation capability, inter-exchange data transfer at very high rates can be achieved since the slips encountered will be very less. This implementation offers level2 network synchronisation capability in MAX-XL.

However SBM-RAX and MAX-L exchanges do not have NSC card inbuilt,therefore Network Synchronisation feature in these exchanges can be implemented by using C-DOT Network Synchronisation Equipment (NSE) as a standalone synchronisation unit.

C-DOT DSS supports CLI and CAMA functions for different applications as Local, Integrated Local cum TAX (ILT) and TAX. When working as local exchange, it is possible to programme the parameters to decide that whether <Area Code> is to be part of Calling Line Identity information or not. If it is Yes, it is possible to programme the digit length as well as sequence of digits in the area code, prefixed to the subscriber directory number. In cases where all the digits are already forwarded in response to CLI request in the form of A4 signal, the additional one or more A4 signals are responded by 0. In otherwords, additional digits as 0 are suffixed to complete CLI information in the network. In case of incoming terminating call when used as local exchange or incoming transit call when used as TAX, the number of digits to be requested from the preceding exchange can be programmed. Accordingly the no. of A4 signals are sent towards preceding exchange. It is also true when CAMA is set for one or more TGPs as well as in case of R2 to CCS7 interworking.

It is possible to programme the CLI information in the network for any specific requirement for different applications as Local, ILT / CLT or TAX.

1. IOPs working in Duplex-mode was very unstable in S/W 2_2_1_3 & 2_2_1_4. This problem has been solved in S/W 2_2_1_6. Moreover, problem of IOP synchronization failure in step 4 & step 5 has also been solved, provided 'tf' & 'bc' group files have been deleted.

2. The problem of Directory Nos. in 'pswd-tmpd' status, when put on 'BNP-ANNC', still getting O/G calls, has been solved in 2_2_1_6.

3. V5.2 links unstability problem has been solved.

4. Metering spurt occurring on I/C TGP counters being used for P.O.I revenue sharing, has been solved in 2_2_1_6.

5. CCS7 signalling working has been imporoved substantially in S/W 2_2_4.3_6 own ward.

6. Call Diversion on Level 1x (except 10x) is made available in S/W 2_2_4.5_6 ownward, to solve problem of 'AMS' accessibility in BSNL network.

7. Subscriber was able to divert his call to Level '95' even if his Access Level has been set to 10x. This problem has been solved.

8. 'Auto-Alarm' functioning not proper in large capacity exchanges specially in Duplex IOP working. This has been solved.

9. Answering Ckt Test not working in CCS7 signalling. Now available in S/W 2_2_4.5_6.

10. Unequipping of BM was not possible in previous S/W release. In s/W 2_2_1_6, crp command 'UNEQ-BM' has been introduced to unequip the BM in IOP Database.

11. Separate Area Code for Access Network (BTS) of different SDCA for 'CLI' purpose can be allotted in S/W 2_2_1_6.

12. Transaction updation in trans files stopping after files reached their maximum block size capacity. This has been solved by reducing themaximum block size to half. Now file will have maximum 10,000 transaction records, after which, previous records will be overwritten.

1. Problem of Bi-lingual announcements has been solved.

2. Access Level 'OG-UPTO-REG' can be given to local PCO with 'Line-Typ = CCB'. In this case, charging of local calls will be done, through 'CRGRTN' defined in system parameter 'PCO-MTR-LCL' while charging on route calls will be done through 'CRG-RTN' defined in the route parameters.

3. Maximum no. of CGSs on one TGP has been incrased from 10 to 40.

4. Subscriber ports going to 'cp-bsy' status and not recovering by normal commands (Problem more severe in 'VU' installed at RSU). This has been solved.

5. Special route '198' (say) not working in main exchange after 'AN-NRM  for 198 configured for any AN-RAX.

6. IOPs unstability (in duplex mode) problem has been fixed.

8. Non avilability of CLI on I/C TGP from Reliance POI connected on CCS7 signalling, has been fixed.

9. 'DBE' (Dialling by Equipment) feature for testing desired trunks using service code '682' has been corrected.

10. ISDN PABX DDI group implementation has been corrected. Now any range of Directory Nos. can be defined and desired no. of digits will be sent towards ISPABX.

11. Problem of null traffic report for Special Routs on Alternate Nos. has been fixed. Now proper traffic report for such routs will be generated.

12. Frequent corruption of level '1' routs (Say 172222) with error "Can't read from file" has been fixed.

13. DGN of 'SS' plane in CM, getting abandoned as SBY 'SSC' goes to 'OOS-SUS' state during DGN. This problem has been fixed in 2216(5.4).