To eliminate a problem in no normal control of equipment though a notice is not output by notifying an arrival of a time of replacing a battery by accurately detecting a lifetime of the battery.

A microcomputer 5 outputs a control code corresponding to a control content input by operating a control key 4 to a transmitter 7, turns on a transistor 8 with '1' of the control code, supplies a current to an LED 9, and transmits an infrared signal. A voltage detector 3 detects an output voltage of the battery 1. The microcomputer decides the arrival of the time of replacing the battery when the current flows to the LED 9, that is, the detected voltage of the detector during a transmitting period of the infrared signal becomes a reference voltage or less of replacing the battery, and a display unit 12 displays the notice of the arrival of the time of replacing the battery.