Patent GB-335278-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/62
Filed: 1929-06-25
Abstract: 335,278. Automatic Telephone Manufacturing Co., Ltd., Beale, C., and Deyes, H. S. June 25, 1929. Automatic exchange systems. -Subscribers at a private branch exchange system are each provided with two outlets over one of which local calls mav be established whilst exchange connections may be set up over the second circuit, these latter connections being completed over combined finder and connector switches provided with breaking-in facilities. In- -coming exchange calls are set up automatically by the operator whose dial is arranged to break a loop circuit when it is associated with the local equipment and to impluse over a single wire when completing an incoming exchange call. When the operator enters an engaged circuit a low tone is connected to the line and the system includes facilities for holding an exchange subscriber calling an engaged extension and automatically connecting to the called circuit when the connected parties clear. Specification 324,954 is referred to. Local call. To make a local call the subscriber connects his instrument to the circuit terminating in the local equipment (Fig. 1) energizing S and enabling LK to operate its light armature lk1. Marking potential is connect to the bank of FS wiped by P1 and G and FDM interact until the calling line is reached. If the connector CS is in its home position E pulls up followed by A and B and LK operates fully. The ringing generator is started up over 15. Dial tone is returned from 16 and the number required is dialled. The numbering range is 1-9, 01-09 and 001-004, terminals 10 and 20 being left unconnected. The dialled impulses are repeated by A to CDM and CS steps to the terminals of the circuit required. Relay E operates in series with CDM and during the slow release pause of E the called circuit is tested by G. If the line is busy G operates and locks and busy tone is returned from 13. If the line is free H energizes connecting ringing from 14. When the called subscriber replies F energizes and switches through. D pulls up over the called loop stopping the ringing machine. When the subscribers clear relays A, B, F, H release and LK and CS steps to its home position. Outgoing exchange call. To make an exchange call the subscriber's instrument is connected to apparatus shown in Fig. 2. ST energizes over the loop and LK operates it light armature lk1 to mark the calling circuit. Relays F and FY operate and FY interacts with FCM until the calling line is reached when FY is shcrted over PI and B energizes. E, which is held in parallel with FCM during stepping, releases and LK and H pull up connecting the caller to the exchange line. Relay A operates in the exchange circuit and holds B. When the calling subscriber hangs up relays A, B, F, H and LK fall back and Z energizes followed by FY. Relay FY interacts with FCM driving FCS to the home contacts. Incoming exchange call. All incoming exchange calls are extended by the operator. When a call is received L operates from the ringing current starting the ringer at l4 and lighting lamp PL. The operator throws keys ANS connecting her instrument to the line and energizing LC and OC. When the extension required has been determined key SD is depressed and the extension number is dialled by DD. The impulses are repeated by IP to FCM and the switch FCS steps to the required position. Relay E is held during impulsing and when the terminals of the line are reached G tests the circuit. If the line is free G remains de-energized and when E falls back H and LK operate connecting ringing from 23. When the called subscriber replies F pulls up and the operator restores her keys to normal. Busy condition-offering a call. If the tested line had been busy G would have operated and locked to the called line, completing an operator's speech circuit to the called circuit and connecting a light tone from Q2 indicating to the subscriber that the operator wishes to offer a call. If the call is to be taken the called subscriber clears releasing G, and H operates ringing the circuit as before. If the caller is required to wait key HK is momentarily depressed energizing HX which contains Land LC. The operator may then restore her keys. When the called party clears the existing connection, G releases and H operates connecting ringing as before and holding HX. When the called party replies F operates releasing HX, L and C and completing the speaking circuit. Local call by operator. By throwing key CL the operator's equipment is extended to apparatus as Fig. 1 and a call may be established as described earlier. The dial DD is, in this instance, bridged across the loop and the springs DD1 short the operator's instrument to prevent clicks during dialling. Night service. The keys NS extend the exchange line to a particular extension for night service. Fault alarm. If fuses blow the relay D (Fig. 1) is energized over 31 operating a fuse alarm over 30. Forced release of connection. The Provisional Specification describes also means for forcing release of a local connection when the line is required by an exchange caller.