Patent GB-227322-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1924-04-05
Abstract: 227,322. Coventry Automatic Telephones, Ltd., and Collyer, J. E. April 5, 1924. Automatic exchange party-line systems.-The same connector is used for regular and revertive calls to the stations on a party-line. The directory numbers of party-line subscribers have an extra digit which controls an auxiliary switch RS to send a particular frequency of ringing current over one or other of the line wires. In the case of revertive calls however the extra digit depends on the calling as well as the wanted station, and causes the switch RS to ring both stations. In the four-party system described, regular calls set the switch RS to one of the first four positions and revertive calls to one of six subsequent positions. In the latter case the switch controls circuit alterations, resulting, when the 'called party replies, in the release of all the switches used in setting up the connection, talking current being provided by a first selector which is then picked up by the line switch. The switch RS may be a relay counting chain or a switch set by more than one digit. Control of ringing-current by the switch RS. The commutators 14 - - 17 are common to all the connectors and make one revolution in six seconds. The three on the left arrange for the. connection of the 16-cycle generator X and the 50- cycle generator Y to the banks swept by wipers 12, 13 of switch RS. The commutator 17 alternately energizes and releases a relay 52 which in its working position connects wiper 12 to the upper line wire and in its resting position connects wiper 13 to the lower line wire. The effect of a particular setting of switch RS can be seen from an inspection of the connections. For example, starting from the position of the commutators shown and assuming them to rotate clockwise, if the switch RS is in its 1st position, no ringing current is sent for the first #-revolution, during the second #, 16-cycle current goes over wiper 13 to the lower line wire, and during the following “-revolution, relay 52 being energized, no ringing current is sent. The cycle is repeated during the second ¢-revolution. Similarly, if the switch RS is set to its 5th position, 16-cycle current is sent in turn over both line wires, and if to its 9th, 16- cycle current is sent in turn with 50-cycle over the lower wire. Setting of connector and switch RS. When the connector is seized, line relay 21 and sluggish relays 23, 26, 28 pull up. The tens digit is repeated to the vertical magnet 1. The change over of vertical springs 7 energizes sluggish relay 31 and arranges for the release of relay 26 at the end of the digit so that the units digit controls the rotary magnet 2. Owing to the change-over of rotary springs 8, the relay 31 falls back at the end of the digit, and the extra digit controls the stepping magnet 9 of switch RS. At the end of the digit, owing to the movement of off-normal wiper 11, relay 28 falls back. Completion of regular call. If the line is busy, relay 39 pulls up and on the relapse of relav 28 is locked up, busy tone being sent from 44. If relay 39 fails to energize, the :relapse of relay 28 extends the release wire to operate the cut-off relay and energizes relay 46 to send out a ringing current as determined by the setting of switch RS in the manner described above. When the called party replies, the tripping relay 56 pulls up and completes the called loop back to the feed relay 65. It will be noticed that during both ringing and non-ringing periods a circuit for relay 56 is completed when the subscriber answers. Release. The relapse of relay 23 when relay 21 falls back energizes the release magnet 3 and completes a self-interrupting circuit for the stepping magnet 9 under control of the off-normal wiper 11. During release, wiper 10 grounds the battery side of relay 23 to prevent its operation in case the connector is prematurely seized. Completion of revertive call. The switch RS being in a position beyond its 4th. the energization of busy relay 39 energizes relay 68 over wiper 10. On the relapse of relay 28, relay 39 is released, relay 68 locks up over the wipers 4, 5 and the calling substation, and relay 73 pulls up, locks itself and cuts off the line relay 21. The calling party now hangs up, and the relapse of relay 68 energizes relay 46 to cause ringing currents appropriate to both calling and wanted stations to be sent out. The completion of the loop, whether during a ringing or a non-ringing period, energizes the tripping relay 56 which locks up and releases relav 23 to initiate the release of all the switches used in setting up the connection. The party line-switch then hunts for a first selector which supplies the necessary talking battery.