PURPOSE: To prevent the kind of a printed circuit board with a built-in control circuit from being increased by unnecessitating a control circuit exclusive for each keyboard.

CONSTITUTION: A keyboard 1 and a signal generating circuit 2 are provided in a keyboard part 5 and for each keyboard 1, respectively corresponding keyboard signals are outputted from the signal generating circuit 2 to a keyboard control circuit part 6. The keyboard signals are received by a signal analyzing circuit 4 in the keyboard control circuit part 6, it is analyzed which type of the keyboard 1 is connected, and the result is outputted to a keyboard control circuit 3 as an analyzing signal. The keyboard control circuit 3 controls the keyboard 1 by outputting respective control signals for each keyboard 1. Thus, the many kinds of keyboards 1 can be utilized by one kind of the control circuit.