GB111174A - Improvements in and relating to Telephone Switching Apparatus. - Google Patents

Abstract

111,174. Kersting, C. B., and Dungey, J. W. Nov. 27, 1916. Intercommunication apparatus.-An electric selector for intercommunication telephone systems comprises a number of turn-keys B mounted upon spindles A which carry at their other ends contact-members C normally held against the stops F by springs SP. When one of the keys is turned it first lifts a conducting locking-bar D thereby releasing any other key already in the operative position and locked there by the engagement of the nose J of the locking-piece with the upturned end of the contact-piece. Further turning of the key brings the end of the contact-piece into engagement with a fixed contact bar E and completes the ringing circuit of the station corresponding to the key. This movement of the contact-piece also brings its upturned end into engagement with the cam-shaped undersurface H of the locking-bar which is consequently raised, considerably, to ensure the release of any previously operated key not liberated by the first part of the movement. When the hand is removed from the key, the contact-piece moves back slightly and is engaged by the conducting nose of the locking-bar thereby completing the listening circuit of the particular key operated. All the keys are returned to the off position by the movement of the switch hook when the receiver in replaced.