Two-wire communication system for interphones

摘要

The system includes a call panel (1) and telephones (T) which are positioned in individual apartments and only have two wires (W1,W2). Each telephone is provided with a CMOS integrated circuit with high impedance and continuous current. A resistance is positioned for low power consumption by each telephone. Each telephone has microswitches which are programmed in binary mode according to a value correlated for each telephone. A train of digital pulses is introduced into a line of each telephone. The format of the pulse train is defined by a first return to zero part followed by a second coding part and an acoustic calling device.