Patent GB-262169-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1925-08-25
Abstract: 262,169. Automatic Telephone Manufacturing Co., Ltd., (Automatic Electric Co.). Aug. 25, 1925. Automatic exchange systems; party-line systems. -In a partyline system using code ringing, means are provided for connecting a calling party to an operator's position when a party-line subscriber is called whose service has been disconnected. The line wires 65 - - 68, Fig. 1, of a partyline, one of the subscribers on which has been disconnected, is connected over a cross-connecting frame CCB, Fig. 2, common to a 100-line group, to a group of conductors 101 extending to and jumpered ,across an intermediate distributing frame IDF to an auxiliary switch AS not in ' service ' at this time. A number of these switches AS is provided comman to the exchange, but the one connected up becomes for the time individual to the party-line 65 - - 68 and is set by the digit which determines the ringing code. The bank contact corresponding to the disconnected party is connected by a jumper 111 to a conductor 114 in order that if the wiper 110 comes to rest on this contact the calling line will be extended over a trunk IT (common to all the switches AS) to an operator's position SB. Normal party-line call. The party-line shown is provided with ten substations A1 - - A10, Fig. 1, five of the substation bells being connected between one line and earth, and the other five between the other line and earth. The code ringer consists of a .distributor D which successively energizes five relays 81 - - 85, which apply ringing current from the generator 89 to five bus-bars 76 - - 80 according to the five ringing codes, the particular code and the line conductor over which it is applied being selected by a code switch CS set by a final digit. The connector C extends connection in the usual manner to the party-line. the switching relay 10 preparing a circuit for a pickup relay 6 and transferring the impulsing circuit to the stepping magnet 73 of the code switch CS, which is set by the final digit. On the relapse of the parallel relay 9, relay 8 is energized, and upon the distributor 87 earthing pick-up conductors 86, the pick-up relay 6 is locked energized and connects the wipers 70, 71 of the code switch CS to the line wipers 51, 54. If the code digit is 1 to 5, the appropriate bus-bar 76 - - 80 is connected to the upper conductor over wiper 70 to ring the bells at substations A1 - - A5, and when the called party replies the ring-cutoff relay 7 is energized over its upper winding and the wiper 71, but if the switch CS is set to positions 6 to 1 the ringing current is connected to the lower conductor over wiper 71 and a return path is provided over wiper 70. On release, when the calling party hangs up, the connector C is restored in the usual manner, and the relapse of release relay 3 also closes a circuit for the release magnet 72 of the switch CS, the relay 8 de-energizing when the off-normal contacts 74 open. Calling a disconnected subscriber on a partyline. Assuming that the subscriber A is out of service, the tenth back contact of the switch AS, Fig. 2, is connected by jumper 111 to the conductor 114. The impulses of the ringing code digit in addition to setting the code switch CS, Fig. 1 are sent by the line relay 2 over a fourth wiper 52 of the connector and conductor 66 to the lower winding of relay 102. Fig. 2, the stepping magnet 108 of the switch AS and a relay 117 of a common relay group RG. The relays 102, 117 pull up, but their low resistance windings do not prevent the response of the magnet 108. If the call is to any substation but the out-of-service one A10, the relay 102 relapses at the end of the digit and energizes release magnet 109 to restore the switch AS, but if the substation A10 is called and the switch AS comes to rest in its tenth position, the relay 102 is held over its upper winding in a circuit including conductor 114, jumper 111, wiper 110, and the earthed release wire 67, and extends the called line conductors 65, 68 to the trunk IT. When ringing current is applied to the called line, an alternating current relay 120 at the operator's position energizes, locks over its upper winding, and lights a call lamp 123. The operator throws her listening key K, thereby unlocking the relay 120 and causing the response of the ring-cut-off relay 7, Fig. 1, over her head-set. She may now converse with' the calling party who releases the connection in the usual manner, the removal of earth from the release wire 67 deenergizing relay 102, which causes the release of the switch AS. The relay 117. which is held up during the sending of the code digit, shortcircuits the lower winding of relay 116 to prevent its operation and the consequent stoppage of the switch AS if the wiper 110 encounters an intermediate contact jumpered to the contact 114 in the case of more than one subscriber on the party-line being out-of-service. If a second switch AS is operated before the first has completed its movement, the relay 117 is held up by the impulses sent to the second switch, and allows this switch to complete its operation. If both calls are to out-of-service subscribers, both will be switched through to the operator, but as this is a remote possibility no provision is made for its prevention. When the impulses of the code digit cease, the relay 117 relapses and the relay 116 pulls up over its lower winding and substitutes its high-resistance winding for the low-resistance winding of relay 117 in the stepping circuit of magnet 108 and the magnets of other switches such as AS as long as the trunk IT is in use. This prevents other switches such as AS from being operated at this time, and also prevents another switch from operating if the existing call is cleared during the impulsing period of another call, since in this case the remaining impulses of the other call will hold up the relay 116.