PURPOSE:To enable to display the voltage drop of battery in the radio remote control unit using key code, by using the transmission confirmation display element providing at the transmitter. CONSTITUTION:The transmitter transmits the signal including the key code by operating the transmission switch 2, and this is received with the receiver and coincidence signal is produced when it is in agreement with the key code of itself and the response unit is driven. The oscillation unit of the radio remote control unit of battery type thus formed is provided with the transmission confirming display element 8 illuminating in response to the operation of the switch 2 and the Zener diode 7 for voltage detection set to be cut off when the voltage of battery 1 lowers to a given voltage. Accordingly, when the battery 1 is more than a given voltage, the element 8 illuminates, but it distinguishes at the voltage below. Thus, the voltage drop can known by using the transmission confirming display element 8.