Abstract: In a telephone system, several telephone terminals are connected to a single telephone line including several telephone interface circuits (6, 7, 8), each interface circuit being energized by ringing signals appearing on the line and being arranged between the telephone line (3) and one of the telephone terminals (13, 14, 15, 16), the ring of which is disconnected from the line. Each interface circuit comprises a circuit (26) for counting ringing signals and picking up the line, this first circuit receiving at the input the ringing signals appearing on the line (L1-L2) during a telephone call, and counting a predetermined number of these ringing signals, then picking up the line by a relay (27) at the moment the last ringing signal counted stops. The system is powered only by the signals on the telephone line.

Abstract: A line powered telephone interface circuit answers an incoming call and, responsive to a command tone, routes the call to a selected terminal. If no command tone is received within a predetermined time period, low voltage audio signalling devices located near the conventional telephone sets are activated to alert the subscriber of an incoming call. The interface need not be connected to a separated supply source. The device is connected to a telephone line and to at least one plug connectable with a telephone set jack, the device being connected to various terminals. A detector detects the ring signal and a relay establishes connection with a telephone line as soon as the ring signal has been detected for a determined time duration. A combination timer/switcher circuit inhibits the ringing of the corresponding telephone set, and is associated with a sound transducer connected operable by a low voltage signal.