GB2114398A - Improvements in or relating to electronic telephone exchanges - Google Patents

Abstract

An electronic telephone exchange of the type which has a switching network operating under the control of main control units and in which control of connections in the switching network is carried out by markers and interrogators. The exchange includes equipment such as a small PABX 23 which provides at least some subscribers with enhanced facilities. The equipment 23 can be activated or de-activated. The exchange also includes a unit 25 which is linked to the main control unit and the equipment 23. The unit 25 is arranged to store data indicative of the enhanced facilities so that the main control units can ascertain which subscribers have enhanced facilities and what those facilities are. <IMAGE>

Description

SPECIFICATION Improvements in or relating to electronic telephone exchanges This invention relates to electronic telephone exchanges. The invention has particular application to exchanges commonly known by the term TXE4 The TXE4 is a known electronic telephone exchange which has a switching network operating under the control of main control units. The connections within the switching network are controlled by markers and interrogators.

It is possible with such an exchange to provide selected subscribers with enhanced facilities such as re-routing of incoming calls. This can be achieved by using a small digital switching device such as a PABX which is linked to the main exchange. In such an arrangement the control unit may wish to know which subscribers have enhanced facilities and which, if any, are activated. The present invention is concerned with an arrangement which makes this possible.

According to the present invention there is provided an electronic telephone exchange of the type having a switching network which operates under the control of main control units and in which control of connections in the switching network is carried out by markers and interrogators, the exchange including equipment which provides at least some subscribers with enhanced facilities which may be activated or de-activated, and a unit which is linked to the main control units and said equipment for storing data indicative of said enhanced facilities whereby the stored data can be accessed by said main control units.

The equipment may comprise a small digital switching device such as a PABX.

The unit may include a RAM which is linked to said equipment so that data indicative of said enhanced facilites can be fed into said RAM.

Afirst highway may link the main control units to said unit to enable said main control units to interrogate the RAM and a second highway may link the unit to said main control units for carrying signals indicative of the result of said interrogation.

The unit may include two sections each with its own RAM and the two sections may be arranged so that operation switches cyclically from one to the other, comparison means being provided to compare the contents of the RAM's.

The invention will be described now by way of example only with particular reference to the accompanying drawings. In the drawings: Figure 1 is a block schematic diagram of a TXE4 telephone exchange; Figure 2 is a block schematic diagram of a TXE4 exchange incorporating the present invention; Figure 3 is a block schematic diagram of part of the exchange of Figure 2, and Figure 4 is a block diagram showing in more detail a circuit used in an exchange in accordance with the present invention.

Figure 1 shows in block schematic form the basic elements of a TXE4 electronic telephone exchange.

The exchange comprises a main switching network 10 which is made up of a number of identical switching units. Each unit is sub-divided into six or eight sections according to the size of the exchange.

These sections are known as sub units and each group of sub units across the exchange is known as a plane. Each termination serviced by the exchange has one connection to each plane in the particular switching unit concerned.

The switching network is controlled by wired-logic markers and interrogators identified by reference numeral 11. The markers can control from one to five sub units whilst the interrogators are provided on the basis of one per sub unit. The markers and interrogators control connections within the switch network and as these are segregated into planes and directly associated with sub units the effects of any fault which may occur is limited.

Also shown on Figure 1 are main control units 12, cyclic stores 14 and supervisory processors 15. The main control units are special purpose processors that use programme control techniques to correlate cyclic-store data and register information. According to the rules set by the stored programme, the main control units establish the required connections through the switching network. A description of the operation of these parts of the exchange will not be given as they are not essential to an understanding of the present invention. In any event their operation will be understood by those skilled in the art and a description of such operation can be found for example in the Post Office Electrical Engineers Journal of January 1976, Volume 68 at page 196, July 1976, Volume 69 at page 68 and April 1977, Volume 70 at page 12.

In a TXE4 electronic exchange of the type just described it is possible to provide enhancements for customers to give them special facilities. One way of achieving this is to make use of a small digital exchange such as that known as the UXD5 exchange. An arrangement which can provide such enhanced facilities is shown schematically in Figure 2 of the drawings. In Figure 2 the TXE4 exchange is illustrated by the block 20 and a subscriber's line 21 is shown linked to the exchange 20 by a detection and access unit 22. The detection and access unit 22 also provides a connection to the small digital exchange which is illustrated at 23 and is connected to the TXE4 exchange 20.By linking certain subscribers to an exchange such as 23 it is possible to provide those subscribers with certain enhanced facilities in a manner which will be apparent to those skilled in the art. An example of an enhanced facility is re-routing of incoming calls. Itwill be appreciated that there may be several exchanges 23.

Having provided enhanced facilities it is desirable to provide some means for enabling the TXE4 exchange to know what is the class of service and on which small digital exchange the enhanced facility is provided. This can be variable information which is stored in the small digital exchange 23. In the present arrangement we propose to provide in the TXE4 exchange a unit which is linked to the highway connecting the main control unit 12 to the markers 11. This unit is indicated by reference numeral 25 in Figure 2 of the drawings and can be interrogated by the main control unit 12 as if it were a marker that is not normally used.The unit can then signal back to the main control unit the particular small exchange 23 which is being used together with the current state of the subscriber's enhanced facility so that the main control unit 12 can determine the method of handling the call and in particular whether to extend it via the small digital exchange 23 or not. Thus, the arrangement provides a means by which the main control unit can be informed of those subscribers which have access to enhanced facilities.

The way in which the unit 25 is linked to the main control unit 12 and the small digital exchange 23 is illustrated in Figure 3. The unit 25 has a dedicted link to a control within the exchange 23 so that the up-to-date facility state held within the exchange 23 is available to the unit 25. Signalling from the main control unit 12 to the unit 25 is by way of a 2/5 highway 30 whilst signalling from the unit 25 to the control unit 12 is by way of a one bit highway 31.

The operation of the unit 25 following an MCU request is essentially as follows. The unit signals the class of service and the customer supplementary services equipment 23 over the highway 31 and this information is received within the main control unit 12. The main control unit 12 upon receiving the information initiates action as follows. If the information indicates that there are no special class of service facilities for the particular subscriber the call is processed as a normal incoming call to the TXE4 exchange. If the information from the unit 25 indicates that a special class of service exists the main control unit 12 receives this information together with an indication of the identity of the PABX 23 to which the customer is connected or in which the customer's data is stored.The control unit 12 can then take appropriate action which includes diverting the call to the particular customer supplementary services equipment such as that shown at 23 in Figure 3.

Depending upon the facility enhancement currently programmed by the subscriber, the equipment 23 take action to complete the call. This can for example, be diversion of the call to a number selected by the enhanced subscriber. Another enhancement is call waiting. In this case the called subscriber may be engaged on a call and the equipment 23 will signal to him via the unit 22 that a call is waiting for him. When the subscriber is engaged on a call with one call waiting no other calls may be allowed to wait.

A subscriber who has access to enhanced facilities can programme his requirements by dialling a predetermined code to the TXE4 exchange. A route is set up from the TXE4 exchange over a junction to the equipment 23 where those requirements are acted upon. For facilities affecting incoming calls to the enhanced subscriber, the equipment 23 updates the unit 25. This is achieved by a control in the equipment 23 via a dedicated data link to the unit 25 in TXE4 exchange. Manual updating of information within the unit 25 can be provided by a teletype associated with the equipment 23 which allows access via the control for the unit 25. Such a teletype is illustrated at 35 in Figure 2.

In the event of power failure automatic reloading of information stored within the unit 25 can be achieved by rewriting of information from the supplementary services equipment 23.

A detailed block diagram of the unit 25 is given in Figure 4. As shown in Figure 4 the unit is effectively duplicated with the top and bottom halves being substantially identical and having a common monitor 40 which is connected by a highway 41 to the equipment 23. Referring to the top half of the unit the highway 30 is connected to a 2/5 receiver 44. The receiver 44 directs information from the highway 30 to a directory number reformattor 45. The directory numberreformattortakes in digits from the time slots on the highway 30 and converts the directory numbers into a parallel format. This number is fed via a 15 bit buffer 46 and used to address a 32K x 8 bit RAM 48. Within the RAM 48 there is stored information indicative of the class of service provided for those subscribers with enhanced facilities.

This information is provided via the dedicated link from the equipment 23 and fed into the RAM 48 via the monitor 40. Thus the RAM 48 can be addressed from the main control unit 12 see Figure 2 via the highway 30 and the result of the interrogation is fed out via an 8 bit buffer 49 and a data selecter 50 to the one bit highway 31. The one bit highway 31 allows the unit 25 to transmit information to the control unit 12 as described above.

The lower part of the unit 25 is identical to the upper half and thus will not be described. The two parts are controlled by counters 55 and 56. The arrangement is such that the counter 55 counts 32 time slots on the highway 30 and then switches control over to the counter 56 which then counts the next 32 time slots on highway 30'. In this way the two parts of the unit 25 work in parallel and the arrangement is such that one provides a monitoring service while the other compares and checks the data. That is to say they alternate with each other to provide on line and checking functions. The comparing function is carried out by the monitor 40 and when it detects a discrepancy the monitor 40 attempts to establish which half of the unit 25 has failed and disables it leaving the other half to continue processing the existing call and all subsequent calls. The monitor 40 will also cause an exchange alarm to be raised. In the event of the monitor 40 being unable to establish which half is faulty it will raise an exchange alarm and place the unit 25 out of service. The existing call and all subsequent calls will be routed through the TXE4 exchange as if no enhancement facility existed. The monitor 40 would then request data from the equipment 23 to arbitrate over which part of the unit 25 is faulty and give an indication of the faulty part.

The part giving a correct response is then placed into service on a permanent basis and the cyclic operation of the two parts is cancelled. The faulty part can then be checked or simply replaced by another board. During removal of a board from part of the unit 25 the alternating cycle and comparison functions are inhibited and services maintained on the operational part of the unit.

Each subscriber with access to an enhancement facility using the equipment 23 has access to a line circuit of the TXE4 exchange via the detection and call access unit 22. The unit 22 is arranged to provide access in the normal state from the subscriber to a line circuit of TXE4 exchange 20. It also enables the subscriber line to be switchable from the TXE4 termination to a line circuit of the equipment 23.

Switching control can be from the unit 23 and directly under subscriber control. A register recall detector can be provided for each subscriber and provision can be made to ensure a false register recall is not initiated during the course of call set up to the line circuit of the TXE4 exchange. The register recall signal is stored in the unit 22 and operates to hold the subscriber's line in the diverted state. The register recall signal causes a call on the TXE4 line circuit to be held by diverting the line to a holding resistor. Line diversions can be reset under the control of a signal from the equipment 23. Application of tones to indicate call waiting are applied from the equipment 23.

CLAIMS (Filed on 4.2.82) 1. An electronic telephone exchange of the type having a switching network which operates under the control of main control units and in which control of connections in the switching network is carried out by markers and interrogators, the exchange including equipment which provides at least some subscribers with enhanced facilities which may be activated or de-activated, and a unit which is linked to the main control units and said equipment for storing data indicative of said enhanced facilities whereby the stored data can be accessed by said main control units.

2. An electronic telephone exchange as claimed in claim 1 wherein the equipment comprises a small digital switching device such as a PABX.

3. An electronic telephone exchange as claimed in claim 1 or claim 2 wherein the unit includes a RAM which is linked to said equipment so that data indicative of said enhanced facilities can be fed into said RAM.

4. An electronic telephone exchange as claimed in claim 3 wherein a first highway links the main control units to said unit to enable said main control units to interrogate the RAM and a second highway links the unit to said main control units for carrying signals indicative of the result of said interrogation.

5. An electronic telephone exchange as claimed in claim 4wherein the unit includes two sections each with its own RAM and the two sections are arranged so that operation switches cyclically from one to the other, comparison means being provided to compare the contents of the RAM's.

6. An electronic telephone exchange substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. Each subscriber with access to an enhancement facility using the equipment 23 has access to a line circuit of the TXE4 exchange via the detection and call access unit 22. The unit 22 is arranged to provide access in the normal state from the subscriber to a line circuit of TXE4 exchange 20. It also enables the subscriber line to be switchable from the TXE4 termination to a line circuit of the equipment 23. Switching control can be from the unit 23 and directly under subscriber control. A register recall detector can be provided for each subscriber and provision can be made to ensure a false register recall is not initiated during the course of call set up to the line circuit of the TXE4 exchange. The register recall signal is stored in the unit 22 and operates to hold the subscriber's line in the diverted state. The register recall signal causes a call on the TXE4 line circuit to be held by diverting the line to a holding resistor. Line diversions can be reset under the control of a signal from the equipment 23. Application of tones to indicate call waiting are applied from the equipment 23. CLAIMS (Filed on 4.2.82)

1. An electronic telephone exchange of the type having a switching network which operates under the control of main control units and in which control of connections in the switching network is carried out by markers and interrogators, the exchange including equipment which provides at least some subscribers with enhanced facilities which may be activated or de-activated, and a unit which is linked to the main control units and said equipment for storing data indicative of said enhanced facilities whereby the stored data can be accessed by said main control units.

2. An electronic telephone exchange as claimed in claim 1 wherein the equipment comprises a small digital switching device such as a PABX.

3. An electronic telephone exchange as claimed in claim 1 or claim 2 wherein the unit includes a RAM which is linked to said equipment so that data indicative of said enhanced facilities can be fed into said RAM.

4. An electronic telephone exchange as claimed in claim 3 wherein a first highway links the main control units to said unit to enable said main control units to interrogate the RAM and a second highway links the unit to said main control units for carrying signals indicative of the result of said interrogation.

5. An electronic telephone exchange as claimed in claim 4wherein the unit includes two sections each with its own RAM and the two sections are arranged so that operation switches cyclically from one to the other, comparison means being provided to compare the contents of the RAM's.

6. An electronic telephone exchange substantially as hereinbefore described with reference to and as shown in the accompanying drawings.