PURPOSE: To control a power feed reed switch with the change of the magnetic force generated when an antenna is expanded or shrunk by providing a magnet on the power feed side of the antenna, and providing the reed switch on a circuit board side.

CONSTITUTION: When an antenna l is set to the shrunk state, the contact piece of a reed switch 4 is pulled by a magnet 2, and a power line is cut off. When the antenna l is set to the extended state, the magnet 2 is moved as the antenna l is extended, the magnetic force is made weaker apart from the reed switch 4, and the contact piece of the reed switch 4 is set to the connected state. The power line is turned on, and the voltage from a battery 5 or an external power source is fed to the circuit of an electronic apparatus via the reed switch 4. The power supply can be turned on or off by extending or shrinking the antenna l, an erroneous action is prevented, and the action quantity of a user can be reduced.