An antenna shaft of an antenna is first inserted through a shaft through-hole created on a lateral plate casing of a stationary-side front case. Then, a flange on the antenna shaft is screw-fixed in a screw hole created at a predetermined position on the lateral plate casing of the stationary-side front case. When the antenna shaft of the antenna is inserted through the shaft through-hole created on the lateral plate casing, an inserted tip of the antenna shaft abuts against a substantially V-shaped connection receiving unit, which is fixed on a circuit board in the stationary-side front case. As a result, an electric connection is established between the antenna and the circuit board.