IE52249B1 - Arrangement for use in connecting telephone exchanges - Google Patents

Abstract

The invention refers to that type of telephone exchange installations which comprises protection relays (17, 18) which when operating current failure occurs shunt the exchange installation (8, 9, 10) and connect an extension (14) directly to an associated telephone line network (15). The invention solves the problem of using such installations when the wish is to interconnect two exchanges through a private or leased line (15', 15') in such a way that one (18') of the relays (11') is controlled by a programmable computer circuit (21', 22', 23') which circuit is connected to an extension line circuit 19'). The arrangement is such that external incoming calls are directed to said extension line circuit (9') while outgoing calls are directed from the central line (10') of the exchange (8') to said network (15').

Description

This invention relates to an arrangement for use in connecting telephone exchanges.

It is often required to be able to interconnect two telephone exchanges, which for example are located in different places, through a line which is not in connection with the public telephone network. Of course a connection can be established between such telephone exchanges through the public network, and if heavy traffic between the exchanges is expected it is often advantageous to establish a connection between the - exchanges directly through a separate line as mentioned above. To adapt the exchanges to each other extensive special arrangements are generally demanded so that the extensions to a respective exchange are able to make contact with each other in a simple manner.

It is desirable that the setting up be carried out automatically.

The type of exchange which is becoming common nowadays is equipped with relay devices which in the case of power failure in the exchange are able to connect one or several extensions outside the exchange directly to the connected network. The relay devices which are to perform this direct connect25 ion can be located on each side of the exchange in question, that is one of the relay devices is connected to the line circuit of the extension and the other to the exchange line circuit. When operating normally - 3 such an exchange with associated circuits is arranged to automatically set up outgoing calls, with an operator manually handling incoming calls. In certain cases it is desirable to utilise the same line to automatically set up incoming as well as outgoing calls to another private telephone exchange.

According to the invention there is provided an arrangement for maintaining a direct connection between telephone exchanges by way of a direct connection telephone line and for providing for a direct connection of one or more telephone extensions to a telephone network in the case of malfunction of one or more of the telephone exchanges, the telephone exchanges each comprising an exchange circuit and having associated therewith a relay circuit, each relay circuit being capable of providing selectively the direct connection of the one or more telephone extension, to the telephone network and the direct connection between the telephone exchanges, the arrangement including control circuits for controlling respectively the relay circuit of each telephone exchange and being connected respectively to a line circuit associated with each exchange circuit wherein the control circuits are programmable and are arranged to analyse received signals so that, for incoming calls to the direct connection telephone line, the control circuits control the relay circuit of one of the telephone exchanges to remain in the receiving position to guide the incoming calls directly to the line circuit of said one telephone exchange and, for outgoing calls, the control circuits actuate the relay circuit of the or another of the telephone exchanges to adopt a position in which a connection is maintained between an exchange line circuit of that other telephone exchange and the direct connection telephone line.

For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:Figure 1 shows how to connect two telephone exchanges to establish an internal connection between them? Figure 2 shows a diagram of a telephone exchange having the exchange line connected to a public network; and Figure 3 shows two telephone exchanges working according to the present invention.

As background to the invention there is shown in Figure 1 a system comprising two telephone exchanges 1 and 2, each being connected to public telephone networks through two lines 3 and 4, respectively. With each telephone exchange there is associated a group of extensions 5 and 6 respectively. It is assumed, for example, that the exchanges belong to two departments of a company located at different places. For traffic reasons it can be inconvenient to load the -public telephone network lines 3, 4 to establish a connection between the exchanges 1 and 2. To do so an internal line 7 is arranged between the exchanges. To make an extension, for example in the group 5, to make contact with an extension in the group 6, shown by dotted lines, no public telephone line has to be utilised but the line 7 can be used. An arrangement according to the above-mentioned is less common in Sweden but very frequent in other countries, especially in those cases when the public telephone network has a limited capacity and it is desired to establish a direct and simple connection between two exchanges.

A type of exchange which is common nowadays and which has a relatively simple construction is shown in Figure 2. The installation consists of an exchange 52248 - 5 8 on the input side of which there is an extension line circuit 9 and on the output side of which there is an exchange line circuit 10. λ relay circuit is arranged which ia connected through a line to the extension line circuit 9 and through a line 13 to an extension telephone set 14. The relay circuit is connected, for example, to an external telephone line network through a line 15, making it possible to connect a line 16 from the central exchange line circuit to the line 15 through the relay circuit 11. The relay circuit 11 comprises two relays 17, 18 the coils of which are connected to a voltage source supplying the exchange 8 with operating current. As illustrated in Figure 2 there is current through the relay coils during operation, resulting in the relays being operated and a connection being established between the lines 15 and 16 and between the lines 12 and 13; that is, the telephone set 14 is connected to the appropriate line circuit of the extension through the lines 13 and 12.

The output side of the exchange 8 with the central exchange line circuit 10 is connected to the appropriate line network. A further extension with the line circuit 19 and the telephone set 20 is shown connected to the exchange 8 and a further central exchange line circuit 10A and outgoing line 15A is , provided. The lines 15 and ISA can be compared with the pair of lines 3 or 4 in Figure 1. The exchange can be handled by operators when appropriate for incoming calls on the lines 15 and 15A.

If, for some reason, the voltage source for the exchange should fail, the two relays 17, 18 will release, resulting in the connection between the telephone set 14 and the line circuit 9 of the extension being broken, while a connection is established between the telephone set 14 and the 2 24 9 - 6 telephone network through the lines 13 and 15, which will then be connected to each other. The line ISA is not included in the relay system.

In practice, however, it would be convenient to be able to use the above-mentioned kind of exchange installation to establish, for example, a connection between two exchanges as indicated in Figure 1 with a possibility of a double automatic set up between them.

Figure 3 shows a solution according to the invention where such a connection has been rendered possible by using an exchange according to Figure 2 to automatically interconnect two exchanges of the type described. Parts corresponding to each other in the exchanges have the same designations as in Figure 2, but with prime and bis signs.

As is apparent from Figure 3 there is connected to respective line circuits 9' and 19’ a so-called addressable flip-flop or inport 21' and 21, respect20 ively. These are connected to control systems 22’ and 22, respectively, which control outputs 23* and 23, respectively, the outputs of which, through a respective line 24’ and 24", are connected to the coil of a respective one of the relays 18' and 18.

As shown in the upper part of Figure 3, the relay 18* is operated to provide a connection from the exchange 8' through the central exchange line circuit 10’ to the line 15*. In the lower part of Figure 3, the relay 18 is released, the line 15 being connected, via the line 12 and the contact circuits of the relays 17, 18, to the extension circuit 9.

The lines 15’ and 15 are connected to each other.

It is assumed that the telephone set 20’ is calling The subscriber will be connected through the exchange 8’ for connection to the line 15* as has been indicated with dotted lines. Simultaneously the inport 21* 5224» - 7 receives a signification signal through the circuit 19* which signal is analysed by the control system 22*, which can be a preprogrammed computer. After the signal analysis, the control system 22 transmits an output signal to the outport 23' giving a control signal to the relay 18' to maintain its operation and thus establish a connection between the exchange 8' and the line 15*.

A call coming from the exchange 8' will then be fed into the line circuit 9 which establishes clear condition. Possible signals, for example pulsation signals will then activate in a usual manner the exchange 8 for selection (dotted line), in this case of the extension circuit 19 with the telephone set 20. The signals are now fed also from the line circuit 9 to the inport 21 and from there to the control unit 22 for analysis. The control unit 22 can be an equivalent computer, preprogrammed as the control unit 22*, which is arranged to receive and analyse information and to feed only control signals representative of the extensions being connected to the exchange, and no other signals, to the outport according to a certain program. Consequently it is assumed that such signals have been added to the line circuit 9 and that the circuit 22" has detected the relevant signals and delivered a commanding signal to the outport 23 to actuate a condition thereof in which the relay 18 remains in its released position, that is, keeping the line 15* in connection with the exchange 8 through the line 12" to the extension circuit 19 and the telephone set 20.

It is now assumed that an outgoing call comes from the telephone set 20*. Pulsation signals are transmitted after clearing of the exchange from the telephone set 20*. The signals from the set - 8 20 are intended for the exchange 8*, connected in a similar manner. The exchange 8* will also be controlled so that signals are transferred to the outgoing central exchange line circuit 10. However, these signals also appear at the inport 21, the circuit 22 and the outsort 23". The analysis of the signals will in this case be such that an outgoing . signal of the outport 23 causes operation of the relay 18, so that the central exchange line circuit is maintained in connection with the outgoing line 15. Thus an external connection is established.

When using an arrangement according to Figure 3 it is not suitable to include the extension 13, shown in Figure 2, as the use of the relay functions of the relay 18 does not permit a parallel connection of the extension without involving practical disadvantages when signalling between the exchange and the telephone set. Furthermore the relay 17 is not in use in Figure 3.

Thus, in a simple manner it has been possible to adapt an exchange installation known per se for connecting lines between exchanges, establishment of automatic calls and setting up of connections between the exchanges in question. The described arrangement provides a particularly good economical solution of a problem which otherwise needs relatively complicated circuitry. It is of course not necessary to effect the control system in the manner which has been proposed by arranging inports with computers inbetween. Furthermore in certain cases the relay circuits can be performed as electronic switches.

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Claims (6)

1. An arrangement for maintaining a direct connection between telephone exchanges by way of a direct connection telephone line and for providing for a direct connection of one or more telephone extensions to a telephone network in the case of malfunction of one or more of the telephone exchanges, the telephone exchanges each comprising an exchange circuit and having associated therewith a relay circuit, each relay circuit being capable of providing selectively the direct connection of the one or more telephone extension, to the telephone network and the direct connection between the telephone exchanges, the arrangement including control circuits for controlling respectively the relay circuit of each telephone exchange and being connected respectively to a line circuit associated with each exchange circuit wherein the control circuits are programmable and are arranged to analyse received signals so that, for incoming calls to the direct connection telephone line, the control circuits control the relay circuit of one of the telephone exchanges to remain in the receiving position to guide the incoming calls directly to the line circuit of said one telephone exchange and, for outgoing calls, the control circuits actuate the relay circuit of the or another of the telephone exchanges to adopt a position in which a connection is maintained between an exchange line circuit of that other telephone exchange and the direct connection telephone line.

2. An arrangement according to claim 1, wherein the relay circuits in a stand-by position, when no calls are present, maintain a connection between the direct connection telephone line and the line circuit of said one telephone exchange for receiving calls. 10

3. An arrangement according to any preceding claim, in which the control circuits each comprise an inport connected to a respective line circuit the inport being connected to a computer controlling an output which outport controls the relay circuits.

4. An arrangement according to claim 3, wherein the inports and outports comprise addressable bistable flip-flop circuits.

5. An arrangement according to claim 3 or 4, wherein the computer is programmable in order to analyse, for outgoing calls, the relevant signals to maintain a connection between the exchange line circuit and the direct connection telephone line, and, for incoming calls, the relevant signals to maintain a connection between the direct connection telephone line and the relevant line circuit.

6. An arrangement,for maintaining a direct connection between telephone exchanges by way of a direct connection telephone line and for providing for a direct connection of one or more telephone extensions to a telephone network in the case of malfunction of one or more of the telephone exchanges, substantially as hereinbefore described with reference to, and as.shown in, Figure 3 of the accompanying drawings.