COPPLING SYSTEM FOR AN ANROPS, PORTTELPHONE AND PORTUGUESE DEVICES

摘要

The circuit arrangement has means for preventing clicking noises during the actuation of the speech direction changeover relay (S) provided in the central station (Z). To generate the ringing signals for the home telephone stations (I, II), 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) assigned to the home telephone station (I, II), a speech wire (10) serving as a return line to all home telephone stations which can be connected to earth (-) by switching means (22, 23) which respond to ringing signal voltage but not to speech signal voltage. To prevent a call which is being made between a home telephone station (I, II) and the door station (T) from being overheard, interrupted or interfered with by other telephone stations, a connection relay (A) is provided in each home telephone station (I, II). When a home telephone station (I, II) is called, the holding circuit (10, al, ERtI+II, 13) common to all connection relays is briefly interrupted and only the connection relay (A) of the called home telephone station (I, II) is activated. IMAGE