Patent GB-191229357-A (GB)
Title: Improvements in or relating to Telephone Systems.
Filed: 1912-12-20
Granted: 1913-12-18
Abstract: 29,357. Automatic Telephone Manufacturing Co., [Antomatic Electric Co.]. Dec. 20. Exchange systems.-Relates to a cord circuit which may be used to connect with magneto or local battery manual lines, with common battery manual lines, or with trunk lines leading to or from an automatic exchange. The cord is divided by condensers 29, 30, Fig. 2, and the supervising-arrangements are identical on each side, the answering plug being connected to a pair of relays 33, 34, operating similarly to the relays 129, 130 connected to the calling plug. The two windings of the polarized relay 34 are normally bridged direct across the cord, but when the relay 33 is energized the battery is cut in between the two windings of the relay 34 so as to supply microphone current in the common battery system. Local battery working. When the answering- plug p<1> is inserted in the jack j<3> of a local battery line A<3>, the cut-off relay 25 is energized, but its resistance prevents the initial excitation of the relay 33, the right-hand winding of which is short-circuited over contacts 115, 113. The two coils of the polarized relay 34 are thus bridged across the cord, so that when the ring- off signal is given, the relay 34 opens contact 113, thus removing the short-circuit around the right-hand winding of the relay 33, which energizes and opens the short-circuit at contact 115 also, so that 'it remains energized and completes the circuit of the clearing-lamp 32 over contact 113. The lamp 121 is controlled similarly by the called subscriber through the relays 129, 130. Common battery working. When the plug p' is inserted in the jack j<4> of a common battery line A<4>, the cut-off relay 12 energizes in series with the relay 33, which by attracting its armatures 117, 118, bridges the battery through the two windings of the polarized relay 34 across the calling line, thus supplying microphone current. The direction of this current is such that the relay 34 opens the contact 113, thus preventing the lamp 32 from glowing. When the subscriber hangs up, the relay 34 closes contact 113 and lights the lamp 32. Automatic working. When the calling-plug p<2> is inserted in the jack of a trunk leading to an automatic exchange, the relay 130 (corresponding to the relay 33) receives no current since the bush of the jack is dead. After the wanted line has been seized by operating the impulse-sender 27, the polarized relay 129 energizes in series with the line relay of the connector, the direction of this current being such as to close a contact 125 in the circuit of the lamp 121. When the called subscriber replies, the battery connexions at the connector are reversed in known manner, so that the armature of the relay 129 is attracted in the reverse direction, extinguishing the lamp 121. Connexion of automatic subscriber to jack of manual exchange. When an automatic subscriber A<1>, Fig. 4, removes his receiver, he is connected by his line switch I<1>, operating as described in Specifications 26,301/06 and 1423/10, to an idle selector E'. To call a distant manual exchange, he raises the selector to the required level, as described in Specification 1298/10, when it rotates to find an idle junction to the manual exchange. When the side-switch passes into its third position, the relay 311 is energized over the calling line, and bridges a coil 317 across the trunk, thus operating the line relay 318, and lamp 319. The operator then proceeds in the same way as when answering a manual line. Selection of automatic subscriber. This proceeds under the control of an automatic subscriber or manual operator in known manner, the group selectors operating as shown in Specification 1298/10 and the connector operating substantially in the manner described in Specification 15,133/11, except that the tone signalling arrangements are omitted, and the ringing cut-off relay is connected somewhat differently.