| 摘要 |
PURPOSE:To prevent an equipment from being broken down, even in case an external equipment is not connected, by providing a buffer circuit having an output control terminal, and a connector for connecting the external equipment and the buffer circuit, and connecting the connector and the external equipment. CONSTITUTION:A buffer circuit 1 is provided with input terminals 11-14, output terminals 15-18, and an output control terminal 19, and the output control terminal 19 is pulled up by a resistance 5. When the output control terminal 19 is an L level, a level of an input appears in the output terminal, and when said terminal is an H level, the output becomes a tri-state. A connector 2 of an interface circuit has terminals 21-26, and the terminals 21-24 are connected to the output terminals 15-18. The terminal 28 is connected to a GND, and the terminal 25 is connected to the output control terminal 19. A connector 3 of an external equipment side has terminals 31-36 and the terminals 35, 36 are connected to a GND of the external equipment side.
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