PURPOSE: To select plural signal paths instantaneously by applying a potential to lead-out lines connected to fixed electrodes of a changeover switches, and providing a selecting circuit which uses the potential as a control signal.

CONSTITUTION: A lock type changeover switch 1 has a movable electrode 10 grounded through a lead-out line and the fixed electrodes 3a∼3d connected through lead-out lines to control input terminals D1∼D4 of a multiplexer 16 respectively. One-side terminals of pull-up resistances 17∼20 are connected to the power supply voltage +B of the circuit and the other-side terminals are connected to the control input terminals D1∼D4 of the multiplexer 16. A pulse obtained by shaping an AC power supply signal is applied to a clock input terminal 21 and the multiplexer 15 is driven by the pulse. A signal output terminal 22 is connected to one of signal input terminals in a group 2 invariably in the multiplexer 16.