The first filter circuit 35 and the second filter circuit 36 will now be described below. As illustrated in FIG. 3, the first filter circuit 35 and the second filter circuit 36 are disposed on the first surface 47 of the circuit board 33. The first filter circuit 35 is located at a position close to the first insertion hole 51A and the second insertion hole 52A on the first surface 47. The second filter circuit 36 is located at a position close to the second peripheral edge 42 and the first insertion hole 51B. The first filter circuit 35 and the second filter circuit 36 form part of a noise reduction circuit 63 illustrated in FIG. 4. For the sake of simplification, the first filter circuit 35 and the second filter circuit 36 are illustrated as rectangles in FIG. 3.
