PURPOSE: To make a signal detecting pen and a cable small-sized, and also to raise an operability of a device by constituting so that a switching signal and a position information detecting signal of a tablet surface are sent to a body from the signal detecting pen by the same common signal line.

CONSTITUTION: In case when a signal detecting pen 30 does not abut on a tablet 62 and a detecting rod 39 is reset forward, a pen switch 44 is closed, an impedance of a cable 45 becomes zero, and voltage (v) of a signal line 47 always becomes zero. On the other hand, when the pen 30 abuts on the tablet 62, the switch 44 is opened, the impedance becomes high, and voltage V0 determined by a voltage dividing ratio of resistances R1, R2 is applied to the signal line 47, and v=V0. Accordingly, make and break of the switch 44 can be detected from a voltage variation of the signal line 47. An impedance converting circuit 51 is connected to the signal line 47, and voltage V of the signal line 47 is outputted as it is in a low output impedance state.