GB162748A - Improvements in or relating to intercommunication or like telephones - Google Patents

Abstract

162,748. Stott, W., and Telephone Manufacturing Go. (1920), Ltd. Jan. 29, 1920. Keyboard switches; switches, locking and unlocking.-In an intercommunication telephone system in which the selector keys take the form of push buttons A, an additional key D is provided at each station, having two operative positions and an at-rest position. After the additional key D has been fully depressed to its second operative position, subsequent operation of any press button A releases the key D to its first operative position. Preferably the additional key D is of the mushroom spring-return type provided with an extension of two diameters D<2>, D<3>, Fig. 5, which serves to actuate the contacts in the two positions. Two rockers E and F engage the mushroom portion D' of the key to lock it in the two positions. The selector keys A are of similar type and are provided with common, locking and ringing bars B, C respectively. The bars B and E are so connected by links G<1>, G that the depression of a key A releases the key D to its first position. The bars B and F are connected to a rocker H. through levers B<1>, H<2> and F<1>, H<3>, so that replacement of the handset on the cradle causes the release of all the keys to their at-rest position.