PURPOSE: To normally continue the transmission of data through the entire area in a loop except a faulty area without prolonging the propagation time of signal even in the case of occurring a fault.

CONSTITUTION: In a data transmission system where the data are transmitted and received through plural stations 11 connected together in a loop shape, a station 111 serving as a transmitter transmits the data to its both adjacent stations 112 and 11n. Meanwhile other stations including both stations 112 and 11n receive the data transmitted from the station 111 and each of these station decides the validity of one of both adjacent stations that transmits the data earlier and inhibits the reception of the data transmitted from the other station. These transmitted data are fetched by the corresponding station and at the same time are transmitted to the station of the opposite direction after amplification. Thus the transmission of data is possible even if one of both adjacent stations or a transmission line has a fault.