GB382635A - Improvements in or relating to manually-operable selecting switches for use in intercommunication telephone systems - Google Patents

Abstract

382,635. Switches held set and freed mechanically. ASSOCIATED TELEPHONE & TELEGRAPH CO., 1033, West Van Buren Street, Chicago, U.S.A. July 28, 1931, No. 21530. Convention date, April 27. [Class 38 (v).] Switches, latching and unlatching.-A manually-operated line-selecting switch in an intercommunication telephone system is constricted by adaptation of the standard fingeroperated dial switch employed in automatic telephone systems, the selector being automatically latched after operation until released by replacement of the telephone receiver. As shown in Fig. 1, the selecting switch is operated by the usual rotatable finger hold plate 55 of the standard dial switch such as is described in Specifications 234,036 and 237,290, [both in Class 40 (iv), Telephones &c.], the operation of which rotates a spring contact finger 68 over spaced contacts 71 corresponding to the different lines in the system. The switch is automatically locked on being moved to engage any particular contact by means of a pivoted spring-controlled detent 80 having a projection 82, Fig. 3, adapted to ride over the teeth of a gear wheel 62 during the switch-operating movement and retain it in its displaced position, This detent is released by the replacement of the receiver between the jaws 8, the weight of the receiver operating switch-hook contact members 17, 18 as described in Specification 253,709, [Class 40 (iv), Telephones &c.], and also depressing a rod 19 which in turn rocks a pivoted plate 22 having a projection 27 engaging a down-turned extension 81 of the detent 80 which is returned under the action of a spring 58 at a speed controlled by the usual governor mechanism 64. To prevent possible damage to the gear wheel 62 due to the sudden re-engagement of the detent projection 82 during the return movement a spring-controlled trigger 87 is provided to engage automatically behind the projection 81 of the detent 80 on its release so that if the receiver is raised during the switch return movement the plate is held away until the trigger is engaged by a pin 91 carried by the moving parts which draws aside the trigger. Similarly if the selecting switch is operated before the receiver is lifted the trigger engages below the projection 81 and prevents the switch being latched in a selected position. In the circuit diagram shown in Fig. 6 the lines are connected to the contacts 1 .. 10, the line corresponding to the local telephone being connected by a lead 97 to the normally-engaged contact 70 of the selecting switch. The switch 17, 18 breaks a ringing circuit through a buzzer and completes a talking circuit, a local talking battery beng connected through a high impedance M. A pushbutton switch 75 is provided to produce on depression ringing impulses at a selected receiver after selection of the line has been effected.