Patent GB-147610-A (GB)
Abstract: 147,610. Western Electric Co., (Assignees of Polinkowsky, L.). Feb. 20, 1919, [Convention date]. Semi-automatic exchange systems; metering- systems.-In a system in which a calling line is extended to an operator's position by automatic switches, the metering-circuit is prepared by the operator and subsequently completed automatically when the connexion at the operator's position is released. In the system described, a calling line on an automatic satellite is connected by line-finders to a two-wire trunk 250 extending to a manual exchange, and the depression of the operator's metering-key 263 connects a high-potential battery 256 to the two-wire trunk, thereby energizing a marginal relay 246 at the satellite, which relay energizes a self-locking relay 239, which prepares the circuit of the metering-battery 249, this circuit being completed during release as the sequence switch 220 runs through positions 15 to 17. Line-finders. When a subscriber removes his receiver, he is connected in known manner by two finders in cascade to the outgoing end of the two-wire trunk to the manual exchange. In order to reduce the number of second finders hunting during slack hours, these finders are arranged in pairs in such a way that only one finder of the pair is able to hunt at the same time. Release arrangements when two finders simultaneously make connexion with the calling line are described later. Extension of call to manual exchange. When the second finder is arrested, the switch 220 moves into its fifth position, closing circuits (1) for a relay 235, which connects the calling line to the supervisory relay 228 and repeater 237, and (2) over the two-wire trunk for the line relay 251, relay 239 not being energized owing to the resistance 242. The insertion of the answering- plug completes a further circuit for relay 239, which now energizes and moves switch 220 into its twelfth position, in which the left-hand winding of a release relay 225 and a marginal relay 246 are bridged across the two-wire trunk. The operator enquires the connexion desired and makes it in the usual way. Release without metering. If the connexion is not completed, the operator withdraws the answering-plug, de-energizing relay 225, thus removing a short circuit around relay 232, which moves switch 220 into its eighteenth position, all circuits being opened. The switch 220 is moved to normal when the linked finder is taken into use. Release with metering. If the connexion is completed, the operator depresses key 263, thereby energizing relays 258, 253, the latter connecting a high-potential battery 256 across the trunk to energize the marginal relay 246, which energizes the self-locking metering-determining relay 239. At the end of the conversation, the operator withdraws the answering-plug, de-energizing relay 225 to move the switch 220 into its eighteenth position as before. As the switch moves through positions 15 to 17, the metering-battery 249 is connected over contact 244, armature of metering-determining relay 239, contacts 243, 233 to the subscribers c-lead and meter. Premature release when two second finders simultaneously connect to calling line. In this case, the high-resistance right-hand windings of the test relays 234 of the two finders are energized, and move the respective switches out of position 1. thereby disconnecting these high-resistance windings. The low-resistance windings of these relays are unable to maintain the relays energized if two are connected in parallel to the same test terminal 230, and the relays 234, 232 are therefore de-energized at once. The relav 232 completes a circuit for a relay 224, which locks up at first over contact 248 and then over relay 232, which moves switch 220 into its 18th position.