To facilitate connection between each instrument component member and a printed circuit by letting a rigid printed circuit board cooperate with a protection cover in which a connector fit-in recessed part in formed.

A protection cover 45 is attached thereto while a rigid printed circuit support 36 is held in the back side of a lower housing 35, and a connector fit-in recessed part 46 is formed in the inside of the protection cover 45 so as to be formed into an electrical connecting part. A connector 47 to which external electrical wires are connected, is fitted in the connector fit-in recessed part 46, and the external electrical wires 57 are brought into contact with the terminal 43 of the printed circuit 36. A reinforcing rib 54 is integrally formed with the outer side of the connector fit-in recessed part 46. This constitution thereby eliminates the deformation of the connector fit-in recessed part 46, allows the connector fit-in recessed part 46 to be formed with high accuracy in dimension, and also allows the contact high in accuracy to be expected between a contact shoe 56 and the terminal 43. And the inner diameter of the connector fit-in recessed part 46 will never be changed in dimension, even if the printed circuit support 36 is dispersed in thickness.