A door lock drive controller, after outputting a drive signal to a drive circuit of a door lock actuator based on a signal from a remote control terminal, outputs an answer back signal in the form of pulses to a lamp drive circuit to light a hazard lamp. In a buzzer drive controller, pulses are converted to waveforms with changing voltage values at a waveform converter. A repetitive pulse with frequencies that changes is generated by a frequency generator based on the waveform-converted pulses and, in accordance therewith, a buzzer is driven by an output unit. A whistle-like tone can be obtained by causing the frequency of the repetitive pulse to change in the direction of increase.