Patent GB-161168-A (GB)
Abstract: 161,168. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Willis, B. D.). March 29, 1920, [Convention date]. Automatic and semi-automatic exchange systems.-A line 2, 3 from an automatic main exchange to a large automatic private branch exchange terminates at the latter exchange in jacks J<1>, J<2>, J<3>, Fig. 1, and in a selector E, Fig. 2. Certain subscribers of the branch exchange are given five-figure directory numbers, and can be called from the main exchange without the intervention of an operator, the connection being completed by the selector E and a connector H, Fig. 3, but the majoritv of calls are to the branch exchange as a whole (net to any individual subscriber) and are effected by dialling a three-figure number ending in O. In this case, the selector E is raised to its tenth level and starts an associated hunt:ng switch C, which lights a signal lamp such as L<3>, Fig. 1, individual to the line 2, 3 at an ide operator's position, and the operator plugs her circuit O into the jack J<3> and ascertains what connection is required. The act of plugging into the jack J<3> restores the selector E to its normal position, enabling the operator, by means of her impulse sender S, to control the selector E and connector H to complete the connection. In the case of calls made without the intervention of an operator, the operation of the switches E, H takes place in known manner, under the ccntrol of impulses in the loop circuit formed by the incoming wires 2, 3, but in the case of calls set up by the operator's sender S the impulses are transmitted over circuits 4 and 89 independent of the talking circuits. Signalling an idle operator. The contacts in the tenth level of the selector E are connected to relay sets, such as 92, 93, which merely serve for holding the selector when it reaches an idle set of contacts. At the tenth level, moreover, contacts 64, 65 are closed, so that a relay 100 is energized and completes a circuit through the stepping-magnet 102 of the switch C in series with a highresistance relay 101. The test wiper 104 is connected to a point between these two magnets, so that as long as the wiper rests on the grounded terminal of a busy operator's position, the relay 101 is short-circuited. The magnet 102 therefore advances the switch C until it reaches an idle operator's position (say the third operator's), whereupon the relay 101 becomes energized and connects ground to both wipers. A circuit 16 is thus closed to energize the call lamp L<3> in series. with a pilot relay 7, which lights a pilot lamp L<4> and grounds the test wire 10. Restoration of the selector E. The operator plugs her circuit O into the jack J<3>, thereby connecting her telephone set across the wires 2, 3 and grounding the sleeve circuit 4 to energize a relay 52, Fig. 2, which energizes a relay 53 (over the tenth-level off-normal contact 64), which locks itself up and energizes the release magnet 60. The restoration of the selector unlocks the relay 53, which energizes a relay 54. The relavs 100, 101 and the lamps L<3>, L<4> and relay 7 are also now de-energized, but the switch C remains in the position to which it was set. Operation of the selector E and connector H by the operator. The first set of impulses from the sender S are repeated by the relay 52 to the vertical magnet 59, and an idle connector in the selected level is then found in known manner and the switching relay 58 is energized. The second and third sets of impulses are repeated by the relay 52 over a circuit 81, 89 to the vertical and rotary magnets 159, 158 of the connector, which completes the connection and tests and rings the wanted line in known manner. Release. The release of the connection is at all times under the control of the calling subscriber, but to enable the operator to correct mistakes, a release key K<3>, Fig. 1, is provided, by which the relay 53 can be energized over the circuit 16 to energize the release magnet 60 of the selector E.