To easily and inexpensively cope with an increase in train straight pull electric control wiring by arranging a converting circuit which performs parallel-serial conversion on a voltage energized condition of train straight pull electric control wiring of one rolling stock between adjacent rolling stocks and performs serial-parallel conversion on the other rolling stock.

Train straight pull electric control wiring 11a of an A rolling stock is energized by closing of a connected switch or the like, and when train straight pull control wiring 11b of a B rolling stock is not energized, AND is made by a logical circuit 15a of the A rolling stock on the fact that energization of the train straight pull electric control wiring 11a of the A rolling stock and a circuit switch 13a of the A rolling stock are not turned on, and a transmitter 18a sends an ON command signal of a circuit switch 13b of the B rolling stock by performing parallel-serial conversion. This signal is transmitted to a receiver 16b of the B rolling stock through inter-rolling stock transition electric connecting wires 17a and 17b, and serial-parallel conversion is performed, and when the circuit switch 13b of the B rolling stock is turned on, and the train straight pull electric control wiring 11b of B rolling stock is energized.