In order to magnetically shield the transmission line which connects the external connector mounted on the outer housing with the internal circuit and also to make it possible to freely mount the external connector without being limited by the position of the internal circuit, an outer housing 60 consists of an outer housing main body 61 and a shielding layer 62 applied to the inner-periphery surface of the outer housing 60. An transmission line 73 extends from the internal circuit through the outer-periphery side of the shielding layer 62 of the outer housing 60 along the shielding layer 62 to the desired position, where the external connector 70 is placed.