To standardize parts, to improve assembly work efficiency and to transmit a correct data signal at high speed by sequentially and repetitively connecting signal lines divided into lengths corresponding to the prescribed number of device groups through a reception circuit or a relay drive circuit, which are installed in a direction where the signal is transmitted.

Individual motors 3 fitted to respective spindles 2 arranged in a spindle rail 1 are driven by individual inverters A8 (A7). Micro computer circuits A8a control the inverters and control the communication of stations and lay two power feeding systems 14, and three bi-directional control signal line A11a, data signal line A11b and common line A11c in series. Since the micro computer circuits A8a transfer a bi-directional signal, they are connected by a drive circuit and a reception circuit. Thus, the signal can inexpensively be transmitted between the devices of respective stations which require the transmission of the signal such as a spinning machine and the synthetic controller 5 of a master station.