PURPOSE: To unify the arithmetic circuit and the check circuit to simplify the circuit constitution by adopting the cyclic redundancy check system to the control system which can be applied regardless of the code structure for the data transmission and other purposes.

CONSTITUTION: Operational registers (shift registers) 1, 2 and 3 are installed, along with first exclusive logical sum circuit 4 which secures the exclusive logical sum between the output of final register 3 and the input data of input-side register 1 and the supplies the output to register 1. In addition, inverter 9 to invert the output of circuit 4, exclusive logical sum circuit 5 to secure the exclusive logical sum between inverter 9 and register 1, and exclusive logical sum circuit 6 to apply the output of circuit 5 to register 2 and then secures the logical sum between the output of register 2 and the output inverter 9 are added. Then the output of circuit 6 is applied to register 3. Register 1, 2 and 3 are preset to logic O prior to start of the operation