GB656191A - Improvements in or relating to automatic telephone systems - Google Patents

Abstract

656,191. Automatic exchange systems. WESTERN ELECTRIC CO., Inc. Feb. 20, 1948, No. 5087. Convention date, March 16, 1940. [Class 40 (iv)] In a cross-bar system, substantially as described in Specification 656,190, a line 13, Fig. 1, is multiplied to a finder switch 5 and to a final selector switch 6 and the corresponding hold magnets in both switches are operated when a call is originated. A link 7 is taken into use for a connection and is released if the connection is not completed within a predetermined time interval. In a revertive call on a party line, the exchange switches are released when the called party replies but no new calls can be made over the party line whilst it is busy. General operation, Fig. 1. When a subscriber 13 makes a call, select magnet 15 and hold magnets 16, 17 are operated under the control of a marker 12, a link 7 is selected to extend the connector to a switch 8 and the line is connected to a recorder 11 and to the marker 12. The recorder 11 records the dialled digits and the marker 12 selects a junctor 9 and completes the connection to the called subscriber 14 over the final selector 6. Detailed operation, Fig. 2. A calling line is marked by operation of a line relay 30. The select magnet 22 and the hold magnet 23 in the finder (5 in Fig. 1) are operated by the marker. The corresponding hold magnet 27 in the final selector (6 in Fig. 1) is operated over a contact of 23. Dialling tone is now provided from a generator 35 and the dialled digits are received by a pulsing relay 34 in the recorder. The select magnet 37 and the hold magnet 42 of the called party are operated in T along with 40 in CO. The marker and the select magnets release together and the called party is rung. The hold magnets 23, 40 are held over the sleeve wire when the called party replies. Time control. Relay 44 operates with 23, 49 being already operated, and both are held over a contact of 45. Relays 44, 45, 46, 48 and 47 operate in sequence, the last three being slow to operate. The hold on relays 44, 23 is removed when 47 operates at the end of a sequence and if 27 is not held over the sleeve wire on completing the connection, it releases, line relay 30 re-operates and hold magnet 27 is still held to keep open the marking lead 31. Party line, revertive calls. The called line tests busy, conductor 50 being grounded and conductor 51 being open at contacts of hold magnet 27 in the switch T. A marker relay is operated over conductor 50 and if the called and calling lines are the same, a ringing circuit is seized and operated. When the called party replies the connection is released, leaving operative only hold magnet 27 and line relay 30 till the call ends.