System for transmitting auxiliary signal in a multiplex communication system

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.