COPPLING SYSTEM FOR AN ANROPS, PORTTELPHONE AND PORTUGUESE DEVICES

摘要

In this circuit arrangement for a ringing, door intercom and door-opening system, the speech direction changeover relay (S) provided in the central station (Z) is actuated via a control circuit (12, 13, 17) which is separated from the speech circuit (10, 11) to prevent clicking noises. To generate the ringing signals for the home telephone stations, a ringing signal generator (G) is provided in the central station (Z) whose ringing signals are fed to a called home telephone station (I, II) via a ringing wire (17, 18) assigned to the home telephone station, a speech wire (10) serving as a return line to all home telephone stations (I, II) which can be connected to earth by back-to-back diodes (22, 23) which respond to ringing signal voltage but not to speech signal voltage. IMAGE