PURPOSE: To decrease the number of input terminals to an equipment controller, by converting key operation information into a key code through a controller dedicated to a key matrix, and outputting it to the equipment controller for a specific time.

CONSTITUTION: The key controller 4 which uses a microcomputer converts 16 kinds of key information into four-bit parallel codes. A four-bit SW code is supplied to a deck controller 2 which controls a cassette deck as the equipment controller or tuner controller 3 which controls a tuner. The controller 4 reduces all the SW code to "1" when none of key switches SW of the key matrix 1 is pressed, but outputs an SW code corresponding to a key SW for the specific time when the key is pressed to reduce all the output terminals to "1" again. The SW code consists of four bits, so only four I/O terminals D0WD3 are used exclusively, reducing the number of input terminals.