Patent ID: 8548068

Claim:
A method for transmitting discrete electrical signals from at least one transmitter to a receiver connected to a two-wire communication line with a voltage supply source, where a reading signal is determined as a logic zero and one by a level of signal in the communication line, relative to preset thresholds, where the receiver is provided with a current sensor installed in the communication line between the communication line voltage supply source and the transmitter nearest thereto, the signal transmission being exercised by the transmitter changing the current in the two-wire communication line owing to the transmitter's output resistance being changed and the sensor measuring the value of the current, said method comprising: providing each of the transmitters with its internal secondary power supply charged from the communication line, with the voltage of the communication line power supply decreased prior to signal transmission and restored upon completion of signal transmission, wherein each transmitter comprises a capacitor acting as an internal secondary power supply and connected to the communication line via a diode.