GB2074814A - Reduction of operator involvement in SVI/CNI calls - Google Patents

Abstract

Currently on Service Interception (SVI) and changed Number Interception (CNI) calls, operators have to be involved in the interrogation of the calling party for the called number before routing the call to be subscriber on SVI or providing the changed number for the subscriber on CNI. In the processor system of System X it is possible to y arrange to have two memory banks, one for numbers on CNI and another for numbers on SVI. Also all the changed numbers can be stored in recorded announcement equipment. All calls routed to a number on CNI automatically are routed to the relevant part of the recorded announcement equipment, thus avoiding operator intervention. All calls to a sub on SVI are subjected to a called sub busy or free test. If the SVI sub is busy, busy tone is returned to the calling sub without operator intervention. Only if the SVI sub is free, is the SVI call routed to the SVI operator.

Description

SPECIFICATION Service interception handling arrangements for stored program controlled telecommunication exchange systems Field ofinvention The present invention provides a method of incorporating service interception facilities into a stored program controlled telecommunication exchange system with a minimum of human operator involvement.

Prior art In current telecommunications systems calls involving called subscribers who required their calls to be intercepted or who have changed their directory numbers are routed to human telephone operators.

Telephone operator involvement is required on service interception (SVI) and changed number interception (CNI) calls to allow the operator to interrogate the calling party for the required number. Typically any subscriber who receives malicious calls can arrange to have all incoming calls intercepted by the operator. In the present network all the incoming calls will appear on a manual board position and the human operator answers and checks each call to ascertain if it is a genuine call or not. The operator leaves the originating subscriber parked and talks to the subscriber who is on service interception on a different speech path so that the originating subscriber cannot hear the conversation between the operator and the subscriber on SVI.

Depending upon the reply given by the SVI subscriber, the operator either connects the caller or informs the caller that he cannot be connected. The operator remains associated with the call switch path so that the conversation can be monitored.

Similarly in changed number interception circumstances when a subscriber moves premises to another telephone exchange area anyone calling the old number for a short period is routed to a manual board position.

The aim of the present invention is to reduce to a minimum, the need for operator participation to in the setting up and control of SVI and CNl calls.

The invention According to the invention there is provided a telecommunications exchange having a control arrangement including a plurality of information storage arrangements, a first storage arrangement storing information indicative of the identity of subscriber terminations on the exchange provided with service interception and a second storage arrangement storing information indicative of the identity of subscribers currently busy and the exchange control system is arranged during the performance of a call processing program to compare the called subscribers identity with the information in the first storage arrangement and if the identity of the called subscriber is stored in the first storage arrangement to compare the called subscribers identity with the information in the second storage arrangement and to control the switching network of the exchange to connect the calling subscriber to a manual board position only if the identity of the called subscriber is not stored in the second storage arrangement.

According to a feature of the invention the control arrangement includes a third storage arrangement storing information indicative of the identity of subscriber terminations on the exchange subject to changed number indication and the exchange network includes a network termination connected to recorded announcement equipment and the exchange control system is arranged during performance of a call processing program to compare the called subscribers identity with the information in the third storage arrangement and to control the switching network of the exchange to connect the calling subscriber to the recorded announcement equipment if the identity of the calling subscriber is stored in the third storage arrangement.

Detailed description of embodiment The invention will be more readily understood from the following description of one embodiment thereof which should be read in conjunction with the accompanying drawings. Of the drawings: Figure 1 shows a block diagram of a stored program controlled digital exchange according to one embodiment of the invention, Figures 2 to 4 show the flow diagram of the basic operations required to perform the embodiment of the invention.

Referring firstly to Figure 1, a general discussion on the exchange equipment will be given, before embarking upon the features necessary to accommodate the invention. One stored program controlled digital switching telecommunications exchange suitable for use with the invention is that which has been developed as a collaborative project in the United Kingdom under the name of System X. System Xis designed to be a family of switching exchanges using micro-electronic technology, integrated digital switching and transmission, stored program control and common channel signalling.

The exchange system is designed on the basis of a series of modules, both hardware and software, which permit the provision of a range of exchanges.

In Figure 1 the exchange equipment is segregated into telecommunications related subsystems and the processor su bsyslom. Tne lolocommu nications subsystems TE generally have corresponding software handlers that are run on the processor subsystem PS.

Telecommunications subsystems For a local exchange the sub-systems used are (i) a Subscribers Switching Subsystem SSS, (ii) a Digital Switching Subsystems DSS, (iii) a Message Transmission Subsystem MTS, (iv) a Signalling Interworking Subsystem SIS, (v) an Analogue Line Terminating Subsystem ALTS, (vi) a Network Synchronisation Subsystem NSS, (vii) a Multi-Party Connection Subsystem MPCS, (viii) an Automatic Announcement Subsystem AAS and (ix) a Man-Machine Interface Subsystem MMIS.

The Subscribers Switching Subsystem SSS performs concentration of traffic from a number of infrequently used subscribers lines into heavily used common circuits at a local exchange. It is also used to carry out all the exchange-to-subscriber signalling at the exchange. The software module for the subscribers switching subsystem includes files which define the busy state of the subscribers connected to the subsystem.

The Subscriber Switching Subsystem consists of a software handler and one or more concentration stages depending on the size of the exchange.

Two versions of the concentration stage, both using the same software for transacting with other subsystems, are provided; one uses analogue switching and the other, which we are primarily concerned with in System X, digital switching.

The digital version of the Subscriber Switching Subsystem is provided in a form which matches existing analogue local line networks and analogue customer apparatus, but can be readily adapted to match new digital local line networks and customer apparatus.

The digital concentration stage uses microprocessors to provide some distributed control. Each concentration stage consists of a line circuit, a line controller, a PCM switch, MF tone detector, a tone injector and a parallel-serial converter.

The Line Circuit performs calling signal detection, line feed, supervision ringing, de test access, 2-wire/4-wire conversion and 64 kbitls pcm encoding/decoding.

The Line Controller provides multiplexing/demultiplexing for 32 pcm channels. In addition, it carries out preprocessing of the exchange/subscriber signalling for the 32 lines it serves.

The PCM Switch terminates 2 Mbit/s links from 128 Line Controllers and provides 4096 channel stores, each with an 8-bit receive store and an 8-bit transmit store. The switch operates in a parallel time-switching mode between the channel stores and a pair of parallel highways, one in each direction. The highways operate at 2 Mbitls with 256 time-slots and 8 kHz frame rate; each is 8 bits wide. 240 of these time-slots are available for carrying traffic and the other 16 are used to provide access to the digital 16-channel multi-frequency signalling receiver.

Supervisory tones are injected through the digital switch from a unit located in the concentrator similar to the multi-frequency receiver.

Each Parallel/Serial Converter deals with 30 of the highway time-slots and carries out digital conversion in both directions between the parallel operation of the internal highways and the serial operation of a standard 2 Mbit/s, 30-channel pcm system. In addition, it deals with time-slot 0 synchronisation and provides insertion/extraction of time-slot 16 6 for communication between the Module Controller and the software of the Subscriber Switching Subsystem.

Some subscriber's lines are provided with additional facilities which cannot be handled at the local exchange by a normal Line Circuit, e.g. control of a subscriber's private meter. These are handled by an Auxiliary Circuit connected in series with the normal Line Circuit and controlled by an Auxiliary Controller.

The Digital Switching Subsystem DSS provides switched paths for the calls handled by the exchanges, setting-up and clearing down these paths as required. The digital switching subsystem hardware is described in some detail in Patent Application No. 14409/77.

The Digital Switching Subsystem terminates 2 Mbit/s 30 channel pcm systems, with the individual channels being separately switched as required.

In addition, time slot 16, which is used for signalling purposes, can be semi-permanently switched to an appropriate signalling termination outside the boundary of the Digital Switching Subsystem itself. The ability to reconfigure the signalling paths through the switch to standby signalling terminations greatly enhances the overall security of the exchange.

In pcm systems, the two directions of transmission are quite distinct, and hence the Digital Switching Subsystem has to provide separate paths in each direction for every connection. This bidirectional switching is equivalent to 4-wire switching in analogue systems.

In principle, the main constituents of the digital switch are three unidirectional elements: the Receive Time Switch, the Space Switch and the Transmit Time Switch.

These elements are interconnected by time-divided data buses of highways and they operate under the influence of a Timing Unit and a Control Unit, which is itself controlled from the Processor Subsystem by the software handlerofthe Digital Switching Subsystem.

The operation of the digital switch is secured by duplication of the three switching elements and their highways. As a result, each 8-bit byte (normally a speech sample) has two separate paths through the digital switch with each path being operated with a 9th (parity) bit. A selecting device beyond the Transmit Time Switch performs parity checks on the bytes it receives from the two paths and under normal conditions, it selects either of the two correctly switched bytes for output purposes. Under transitory or sustained fault conditions on one path, it selects the correctly switched byte on the other path as the output. This arrangement is disclosed in some detail in Patent Application No. 14035/77.

The digital switch is further secured by replication of its timing and control elements and by the use of majority logic techniques in these areas.

In practice, a number (n) of time switches are provided on both the receive and transmit sides, with each time switch terminating 32 pcm systems. Within these switches, the 32 time-slots of every pcm system are provided with separate 8-bit channel stores, with each switch having a total of 1024 (32 x 32) such stores.

Each time switch has its own 1024 time-slot highway which connects it to the space switches, and it has the capability of connecting any of these time-slots to any of its 1024 channel stores as required by the space switches.

A highway is a parallel interconnection which is 9 bits wide (8 information bits plus 1 parity bit). As it has an 8 kHz frame rate and 1024 single-bit time-slots, it is essentially an 8 Mbit/s device.

Two space switches are provided, one to handle all the odd time-slots in the highways and the other to handle all the even time-slots. Their alternate operation results in each having to operate at 4 Mbit/s, which is half the speed of the highways. Each provides an n x n interconnection matrix between then receive highways and the n transmit highways.

Considering first one direction of transmission, the function of a space switch is to provide a switched connection between the appropriate receive and transmit channel stores. It does so by providing a switched path by means of parallel crosspoints between the appropriate highways, but only during an allocated time-slot in each operating cycle. This time-slot is allocated by the space switches themselves and subsequently remains fixed throughout the duration of the required connection.

In the opposite direction, the connection is made half a cycle (frame) later, i.e. 512 time slots later. In many cases, the connections required in the two directions of transmission involve completely different highways.

However, in the minority of cases, when a connection is to be made between two channels in the same pcm system or between two channels on different pcm systems but which terminate in the same time-switch, the connections for the two directions of transmission use the same pair of highways and the same crosspoints.

The half-cycle displacement of 512 time-slots between the two switching processes provides the necessary separation between the two paths.

In all cases, to make the central connections which occur within the space switches effective, the receive and transmit time switches operate in synchronism with the space switches and so provide an overall parallel path for the 8 + 1 bits of each speech sample.

The selecting device referred to above completes the switching process by performing the parity checks and then by transferring the 8 bits it correctly received in parallel into the appropriate channel store for serial transmission at2 Mbit/s.

The Message Transmission Subsystem MTS performs common channel signalling functions with error correction and is really used only for inter-exchange working. Accordingly, this subsystem will not be considered in more detail as it is not used in the performance of the embodiment of the invention.

The Signalling Interworking Subsystem SIS provides interface and facilitates for interworking with existing exchanges and systems which use a diverse variety of channel associated signalling systems. The service interception circuit will fall into this category and it will be located in the outgoing junction SIS arrangement connected to the manual board system used to supply the service interception facilities. The operation of this interface will be appreciated during the description of the operations performed later.

The Analogue Line Terminating Subsystem AL TS converts analogue transmission signals, such as speech and other waveforms into digital form and vice versa. Again this subsystem is not significant to the performance of the embodiment of the invention and so it will not be considered further.

The Network Synchronisation Subsystem NSS ensures that an exchange operates at the same average bit rate as the synchronised network as a whole.

At a System X exchange, a 2 Mbit/s link which carries information appertaining to network synchronisation, is routed through a Link Control Unit before being terminated at the Digital Switching Subsystem in the normal way. This unit, which forms part of the Network Synchronisation Subsystem, performs two quite distinct kinds of function; it measures the phase difference between the 8 kHz frame of the incoming 2 Mbit/s signal and the corresponding frame derived from its own exchange clock, and it inserts and extracts coded information which is interchanged between its own exchange and the distant synchronisation centre.

The Network Synchronisation Subsystem assesses the phase measurements by its Link Control Units and the information it receives from other centres and it determines when and what kind of adjustment to make to its own clock. During the periods when it is adjusting the phase of its own clock, it sends appropriate signals to all those distant centres with which it shares mutual synchronism. The Network Synchronisation Subsystem is not significant to the performance of the invention and so will not be considered further.

The Multi-Party Connection Subsystem MPCS enables three or more parties to participate in a telephone conversation. This subsystem is used by the manual board operator to provide the service interception operation particularly when talking to the called SVI subscriber in isolation from the calling subscriber.

The Automatic Announcement Subsystem AAS allows synthesised announcements, as required, from digitally recorded segments of speech to facilitate customer/exchange interactions, particularly those for certain supplementary services such as changed number interception. In this case the speech information indicating the new number is digitally recorded and a call to the old number is re-routed to the automatic announcement subsystem AAS.

To control the telecommunications hardware modules a number of software modules are required and these are located in the processor subsystem PS and are called up as required by the software parts of the telecommunications modules. The software subsystem modules used by the embodiment of the invention are (i) a Call Processing Subsystem CPS (ii) a Call Accounting Subsystem CAS and (iii) a Management Statistics Subsystem MSS.

The Call Processing Subsystem CPS controls the process of each call on the basis of instructions sent by the caller. The call processing subsystem includes a file indicating the identity of those subcarriers which are on service interception (SVI) or changed number interception (CNI). The call processing subsystem is central to the operation of the exchange system and it generates messages which are sent to other subsystems and it receives messages from other subsystems as required by a call in progress. Figures 2-4 show the flow diagram steps required to be incorporated in the call processing subsystem to handle SVI calls in accordance with the invention. These steps will be considered in detail later, together with the intermodule messages required for the SVI call sequence.

The CallAccounting Subsystem CAS controls the charging information for each call handled by the exchange. Typically this subsystem will be informed by the call processing subsystem of the real time of the start and completion of calls handled by that subsystem. This subsystem is only used in a subsidiary manner in the embodiment of the invention and therefore will not be considered in any significant detail.

The Management Statistics Subsystem MSS collects the basic traffic data needed for short and long term planning purposes. This subsystem is not germain to the embodiment of the invention and it has been included only for completeness sake as a record is made in this system for each SVI call made to a manual board.

System Operation on SVlcalls The system operation will be described with reference to Figures 2 to 4 relative to the operation of the call processing subsystem CPS. This subsystem handies the call set-up operations in the same manner for all calls up to the point of sending a "busy path" message to the terminating Subscribers Switching Subsystems. At this point in the call processing subsystems operation the called number will be checked to see if the called subscriber is on SVI. This operation simply involves referring to the SVI/CNI file. This operation is shown at Step S1 in Figure 2. The following detailed description will be segregated under the corresponding steps of Figures 2,3 and 4.

S7 SUB ONSVllCNl? If the identity of the called subscriber is not on the SVI/CNI file, step S1 is exited to continue with a normal call set-up as indicated at Step SX in Figure 2. However if the identity of the called subscriber is on the SVI/CNI file step S2 is performed.

S2 SUB ON SVI? In this step the call processing subsystem decides if the called subscriber is on SVI or CNI. If it is on CNl the call is extended by the DSS to the necessary recorded announcement equipment to convey the new number to the calling subscriber, this is shown at step SY in Figure 2. Calls to those called subscribers on SVI are extended to step S3.

S3 SUB BUS Y? In this step the call processing subsystem sends a message to the subscribers switching subsystem serving the called subscriber to interrogate that subsystem's busy file. If the called subscriber is busy the call processing subsystem signals to the digital switching subsystem DSS to connect the calling subscriber to the busy-tone box, this is shown at step SZ in Figure 2. If the called subscriber is not busy, Step S4 is performed.

S4 SEIZEM.B.

In this step a manual board position is seized. This is performed by sending a message to a selected one of the SVI junction relay sets served by the signailing interworking subsystem SIS serving a junction connected to a manual board position. Typically an SVI junction relay set (DC loop signalling) consists of three polarised relays and a diode bridge arranged so that the polarised relays monitor the potential of the distant end (manual board) and respond to changes of direction of current and changes of resistance. The actual functions provided by the SVI relay set are as follows: a) Idle - Connect a high resistance loop to the distant end and detect 650 ohms earth on the negative leg and 650 ohm battery on the positive leg. In the absence of either condition indicate busy.

b) Seize -To provide a low resistance loop to the distant end and to indicate busy as soon as it is seized.

c) Answer -To detect a 270 ohm earth condition on the negative leg and a 270 ohm negative battery condition on the positive leg.

d)Trunk offer -To detect the absence of conditions (TKO) in (c) e) Transfer -same as (c) (calling sub) f) Transfer -To detect a 270 ohm earth condition (calling sub) on the positive leg and a 270 ohm battery condition on the negative leg.

g) Operator -To detect a 9070 ohm earth on the flashing positive leg and a 9070 ohm negative battery on the negative leg.

The call processing subsystem CPS will now be suspended at step S4 until a message is received from the signalling interworking subsystem SIS to indicate that the "seize" has taken effect at the SVI junction relay set taken into use in this step.

S5SVIRSBUSY The call processing subsystem operation is continued by the reception of the busy signal from the seized SVI relay set causing step S6 to be performed.

S6 SEND RING TONE TO CALLING SUB In this step the call processing subsystem takes the digital switching subsystem DSS into use and connects the calling subscriber to ring tone. The call processing subsystem CPS will again suspend at this point, awaiting the detection of the operator answer condition from the SVI relay set selected for use in step S4.

When the manual board operator answers condition (c) defined above is detected by the SVI junction relay set and the signalling interworking subsystem SIS will generate a message "operator answer" causing step S7 to be performed.

S7 TRIP RINGING In this step the call processing subsystem CPS sends a message to the digital switching subsystem DSS to remove ring tone from the calling subscriber.

S8 CONNECTSVIRS TO CALLING SUB In this step the call processing subsystem CPS sends a message to the DSS to connect the calling subscriber to the SVI relay set and thence to the manual board position. This operation will of course involve an interplay of messages allocating and checking paths as required to set-up the duplex speech connection through the DSS. Upon completion of the connection between the calling subscriber and the manual board position the call processing subsystem CPS is suspended awaiting for the operator to operate the transfer key. At this point in time, the calling subscriber is connected across the DSS to the SVI relay set and then to the manual board position and the operator is in voice communication with the calling subscriber.The operator of course may now ascertain who the calling subscriber wants to speak to and can set-up a connection to the called subscriber to assess if the call is to be extended to the called subscriber. This completes the operations of the CPS in Figure 2 and when the operator has decided that the call should be terminated or allowed to continue the next sequence of operations are shown in Figure 3 S9 CLEAR? In this step the message received by the call processing subsystem CPS from the SIS serving the SVI relay set is tested to see if it is a "clear" message indicating that the call should be cleared down (as indicated in step SW) as the called subscriber does not want the call extended to him. Alternatively if the called subscriber is willing to accept the call, the operator performs a transfer operation and the "transfer" message received from the SIS serving the SVI relay set will cause step S10 to be performed.

The actual operations performed by the operator cause: a) for a rejection of the call, an answer condition to be detected by the SVI relay set or b) for an acception of the call, the operator operates the transfer key which effectively causes an answer condition to be sent followed by an answer condition reversed.

SlO CLEAR CALLING SUB TO SVIRS In this step the call processing subsystem CPS clears down the connection between the calling subscriber and the SVI relay set.

811 BUSY CALLED SUB RECORD In this step CPS sends a message to the subscribers switching subsystem SSS serving the called subscriber and the busy file is updated by entering in the identity of the called subscriber.

S12 SET-UP CALL RECORD In this step CPS sends messages to the call accounting subsystem CAS and the management statistics subsystem MSS to record the accounting and statistical information for the call.

S73 RING CALLED SUB In this step the DSS is instructed by CPS to send ringing current to the called subscriber.

S14 CONNECT CALLING SUB TO MPCB In this step the CPS instructs the DSS to connect the calling subscriber to the multi-party connection box MPCB to provide, ultimately, a conference call involving the calling subscriber, the called subscriber and the manual-board operator.

815 CONNECT SWRS TO MPCB The call processing subsystem CPS instructs the digital switch subsystem DSS to connect the SVI relays set serving the manual-board position to the multiparty connection box MPCB. This completes two-thirds of the conference call connection.

S16SENDRt TO CALLING SUB In this step the DSS is instructed to send ring tone to the calling subscriber indicating that the required party for the SVI call is being rung. The CPS now suspends at this point awaiting a message from the subscribers switching subsystem SSS serving the called subscriber. The CPS sequence is then handled by the steps shown in Figure 4. The message sent by the SSS to CPS should be "called sub answer".

S17 CALLED SUB ANSWER In this step the message received from the subscribers switching subsystem SSS is detected and the call processing subsystem operation sequence is restarted.

S18 CLEAR RINGINGAND RT In this step CPS sends messages to the DSS to remove the ringing current from the called subscriber and ring tone from the calling subscriber.

S19 CONNECT CALLED SUB TO MPCB In this step the last section of the three party conference connection is completed by CPS instructing the DSS to connect the called party to the multi-party connection box MPCB.

S20 RECORD TIMEIN CAS In this step the call processing subsystem CPS sends a message to the call accounting subsystem CAS to indicate the real time at which the subscriber/subscriber connection has been made for call accounting purposes. The call processing system will now suspend allowing the call to proceed with the operator in or out of the multi-party connection as required. The call will be cleared down in a normal manner when either of the subscribers hang-up. Steps S21 and S22 are shown in Figure 4 to accommodate the situation where the operator requires to clear from the connection. Step S21 will be performed upon the reception of an "operator-clear" message from the SIS serving the SVI relay set of the connection.

S21 CLEARSVIRS TOMPCB In this step the DSS is instructed by CPS to clear down the multi-party connection box-to-SVI relay set connection.

S22 CONNECT CALLING TO CALLED SUB In this step the DSS is instructed to re-configure the call removing the multi-party connection box MPCB from the call connection path allowing the call to continue as per a normal call.

This completes the operation of the exchange in the handling of SVI calls. It will be appreciated by those skilled in the art that the embodiment described has been exemplary only and alternative arrangements could have been used to accommodate the features of the invention. For example, the exchange described is a digital exchange having a modular hardware and software construction. However, an alternative arrangement could be provided using an analogue switching network with a single processor control system carrying out all the administrative functions.

Claims (7)

1. A telecommunications exchange having an exchange control equipment which includes a plurality of information storage arrangements, a first storage arrangement storing informaion indicative of the identity of subscriber's terminations on the exchange which are provided with service interception and a second storage arrangement storing information indicative of the identity of subscriber's terminations currently busy and the exchange control system is arranged during the performance of a call processing program to compare the called subscriber's termination identity with the information in the first storage arrangement and if the identity of the called subscriber's termination is stored in the first storage arrangement to compare the called subscriber's termination identity with the information in the second storage arrangement and to control the switching network of the exchange to connect the calling subscriber to a manual board position only if the identity of the called subscriber is not stored in the second storage arrangement.

2. A telecommunications exchange according to claim 1 in which the exchange control equipment includes a third storage arrangement storing information indicative of the identity of subscribers's terminations on the exchange which are subject to a changed directory number and the exchange network includes a network termination connected to recorded announcement equipment and the exchange control system is arranged during the performance of a call processing program to compare the called subscribers identity involved in a call with the information in the third storage arrangement and to control the switching network of the exchange to connect the calling subscriber to the recorded announcement equipment of the identity of the calling subscriber is stored in the third storage arrangement.

3. A telecommunications exchange according to claim 2 in which the second and third storage arrangements are combined.

4. A telecommunications exchange according to any one of the preceding claims in which if the identity of the called subscriber is stored in the first storage arrangement, the exchange control equipment conditions the switching network of the exchange to connect the calling subsoriberto a busy tone generation device.

5. A telecommunications exchange according to claim 4 in which at least one service interception junction relay set connected to a manual board position is terminated on the switching network and the calling subscriber's termination on a service interception call to a free called subscriber's termination is connected by the switching network to a service interception junction relay set.

6. A telecommunication exchange according to any one of the preceding claims in which the switching network operates upon time division multiplexed information in digital form and the manual board positions are located remotely from the switching network.

7. A telecommunications exchange substantially as herein described with reference to the accompany ing drawings.