PURPOSE: To suitably take out a signal for driving an AFT (automatic frequency tuning) defeating circuit by mounting a means for obtaining said signal by using the change of voltage generated between both the ends of any one of resistors at the time of the replacement of contents to be preset.

CONSTITUTION: When the 1st channel selecting switch SW1 is completely turned on, current flows from a resistor R3 to the earth through a preset switch BS1, a light emitting diode D1 and the 2nd switch (b) and the potential of a line l3 is turned to its low level, so that a switching diode d3 is turned on and the voltage of a point (x) drops down to 2.5V. Consequently a positive pulse like A is generated from a means 10 at the switching of channels and an AFT defeating circuit 5 is actuated during the positive pulse period or a fixed period corresponding to said period to stop applying the AFT voltage formed by an AFT circuit 2 to a tuner 1. By said procedure, a signal for driving the AFT defeating circuit can be suitably taken out at the switching of channels.