To prevent damage to an element even though a live wire is inserted or removed, to reduce undesired radiation and to save power of devices by inputting and outputting a signal only when the devices are connected.
When a device 5 to be added is not connected to a basic device 1 in operation, an input-output signal control circuit 4 is not connected to ground GND even though the line of a gate control signal Sg is clamped by a power supply VCC, therefore, the gate control signal Sg is not active and the connection operation of an input-output signal Sa is not conducted. Next, when an external connection terminal A3 is connected with an external connection terminal B7, the line of the gate control signal Sg becomes a circuit form in which the line is connected to the power supply VCC and the ground GND. Thus, the control circuit 4 becomes active, the input-output signal Sa becomes conductive by the trigger of the control signal Sg to be supplied to an external connection terminal A. Then, the internal circuit A2 of the basic device 1 and the internal circuit B of the device 5 to be added transmit and receive the input- output signal.
| JP2002091641 | PRINTER CONNECTOR |
| JPH04260111 | CONSTITUTING METHOD FOR UNIT |
IWAKOSHI NAOKI
HINO YASUHIRO
