Data communication system including a high-speed main channel and a low-speed stand-by channel with high reliability

A data communication system including a main channel that includes means for sending a periodic signal, means for transmitting said signal and means for receiving said signal, the sending means sending signals at a known frequency,

• wherein the communication system includes a stand-by channel that includes the following devices:
• a device for temporarily stopping the sent signal at instants known as stopping instants for a constant length of time that corresponds to the sending of a first determined number of sent signals, the stopping instants corresponding to temporal coding of a stand-by signal;
• a device for summing the amplitudes of the received signals, the summing being carried out on a second determined number of received signals, said second number being less than or equal to said first number;
• a device for temporally determining the instants corresponding to the minima of the summed signals, said determined instants having the same temporal coding as the stopping instants.