PURPOSE: To exchange a crystal oscillator without opening/closing a case tightened with a screw when the crystal oscillator is exchanged according to frequency change.

CONSTITUTION: A local oscillation unit 24 composed of the crystal oscillator 5 required to be exchanged according to the frequency change and an oscillator circuit 6 on a printed circuit board 7 is housed in the housing part 21 of a battery case 3, and it is inserted to a battery housing part 10B with a battery 4. Thereby, an electrode 40 and an electrode 41 in a frequency conversion circuit 11 are connected with each other in a non contact state by electromagnetic coupling, and the crystal oscillator 5 can be exchanged without opening/closing a front panel 1a tightened with the screw.