PURPOSE: To prevent a power supply switch from being carelessly kept at on or off by fitting a pair of electrodes to the contact side with a human body on the back of an enclosure, and closing the power supply switch when the electrodes are connected to each other through the human body.

CONSTITUTION: A mounting detecting electrode 2 and a calling signal sensing electrode 3 are provided on the contact side with a human body at the back side of the case 1 of an individually selecting and calling device and a part other than the electrodes 2, 3 is formed as a case conductive part 4. When the device is not mounted on an arm, the input of an inverter 7 is kept at a high level by a resistor 6, an output, i.e. the control voltage of a power supply switch 8 is turned to a low level and the switch 8 is turned off. When the device is mounted on the arm, a human's skin resistor 10 is connected between the electrode 2 and the conductive part 4, the input of the inverter 7 is turned to a low level, its output is turned to a high level and the switch 8 is turned on. Since the power supply switch can be prevented from being carelessly kept at on or off, power consumption can be reduced and a call can be surely transmitted by the electrode 3.