PURPOSE: To attain cost-down and to save wiring space by connecting a controller main body and an input/output unit with a few signal lines in controlling lots of input and output means so as to reduce the quantity of electric wires for the wiring.

CONSTITUTION: The titled equipment consists of the device main body 50 and lots of register units USR1, USR2... USRn. Each register unit is provided with a serial data input terminal Sin and a serial data output terminal Sout and the register units USR1∼USRn are connected in series with respect to the data line. Control signal lines SLD, CLK1, CLK2 and SEL of the device main body are connected in common to the register units USR1∼USRn in common. Thus, the number of signal lines connecting the device main body 50 and the register units USR1∼USRn is in total as less as 6. An understood clearly in figure, the number of the said signal lines is constant independently of the number of register units to which the input and output means are connected.