PURPOSE: To prevent alteration of train number during operation by indicating the train number as it is if the power interruption time is shorter than a predetermined time.

CONSTITUTION: When trains are made up, power source P may be interrupted before finish of separating work. But since a power source 3 is providing power supply V untill a counter 1 overflows even if the power source in interrupted, the counter 1 functions with no trouble. Since a train number recognizor 10 is storing previously recognized data, the counter 1 does not overflow even if a power source PS is interrupted every time when the trains are separated or jointed if the overflow time of the counter 1 has been set sufficiently longer than the make up time and thereby train number is not recognized automati cally.