PURPOSE: To control a required number of mobiles individually without causing any interference of signals being transmitted thereto by providing the mobile with a variable voltage circuit or a signal decision circuit for transmitting a signal to a direction controller while furthermore providing an ID comparison circuit for controlling the output signal from the signal decision circuit.

CONSTITUTION: A current superposed with pulse-like data codes is delivered on a track to a required number of mobiles 4. The received data codes are separated by a signal separating circuit 22 and recovered by a signal recovering circuit 27. A signal decision circuit 23 then makes a decision whether it is a preset signal or not and an ID comparison circuit 24 controls the output of signal. When a signal is transmitted from the signal decision circuit 23 to a variable voltage circuit 20, speed of one mobile 4 is controlled and when a signal is delivered to a direction control circuit 21, the advancing direction of the mobile 4 is controlled. This constitution allows individual control of required number of mobiles 4 without causing interference of transmission signal.