Abstract: Each sensor of the system is connected to a central station and is interrogated cyclically. In turn, the sensors generate over a bus line a variable amplitude signal synthesized from data stored in a read only memory. Each sensor has a read only memory with different data and thus generates a different waveform during successive intervals of time. Any modification in the waveform of the signal transmitted by a sensor is interpreted as an alarm due to the detection of an intrusion, for example, or due to an attempt at sabotaging the sensor or the bus lines. The complexity of the waveforms synthesized by the sensors makes a simulation very difficult intended to neutralize the remote monitoring system.