Abstract: In a system for exchanging encoded messages between stations, each station comprises a control unit and a connection module connected to a signaling link and a data link, the signaling and data links being serial multiplex links synchronized by a general timebase. Each connection module sends over the signaling link, in a time slot of a frame, four status bits, one reservation bit and one standby bit and receives in its time slot a calling bit from a calling station, or sends a calling bit in the time slot of a called station. The length of the data messages is equal to an integer number of frames, this number having a predetermined maximum value beyond which a watchdog timer disables sending over the information link. Each message is sent in its entirety and without interruption.