Abstract: In an auxiliary signal transmission system used in a multiplex communication system, a first auxiliary signal which is necessary in a transmitting terminal and a receiving terminal is transmitted directly without processing in an intermediate repeater station, and a second auxiliary signal which is necessary in at least one intermediate repeater station is processed in the intermediate repeater station, and thereafter, is transmitted to the receiving terminal. Therefore, transmission discontinuity in the system caused by a fault in the intermediate repeater station can be prevented.

Abstract: A channel-system exchange system for exchanging a channel-system between a main radio-communication channel system and a standby radio-communication channel system without loss of any data and with a high speed, regardless of a phase difference and/or pattern mismatch, on data in the two channel systems.

Abstract: A channel switching system without an instantaneous signal loss in a data communication system such as a digital microwave multiple radio communication system. The channel switching system includes a control unit for generating a switching control signal in response to a fault detecting circuit; a unit for receiving a phase adjustment signal from the active receiver unit of an active transmission channel and another signal from the standby receiver, for adjusting the phases between both received signals in response to the switching control signal, and for outputting a switch energizing signal; a high speed switching unit, including a unipolar high speed switching circuit, for switching signals from the phase adjustment unit in response to the switch energizing signal. The switching system further includes a compulsory switching unit, for compulsorily switching the signals supplied to the switching unit.