PURPOSE: To prevent the production of error signal due to out of synchronism between a control signal and an input signal, by providing a latch circuit at an output of a multiplexer.

CONSTITUTION: A multiplexer 6 selects input terminals 1∼5 according to the 1st control signal of a control circuit 7. A latch circuit 8 is used to latch an output signal of the multiplexer 6, and latch operation is started by the 2nd control signal produced every time when the 1st control signal of the control circuit is switched. The 3rd control signal to release the latch operation is produced, when an output signal of the multiplexer 6 changes after a prescribed time from the latch operation start based on a signal obtained through giving delay the 2nd control signal with a delay circuit 9.