PURPOSE: To obtain a device executing data communicating among many computers with small power by adding a signal switching circuit section and a control signal converting circuit section to a signal amplifier section to reduce power losses.
CONSTITUTION: The signal amplifier circuit section 1 consists of a PNP transistor (TR) 4 and an NPN TR 5 and uses a transmission signal line 2 as the input. The signal switching circuit section 11 is provided between the signal amplifier circuit section 1 and a transmission line 3 and consists of a P channel MOSFET 12, a diode 13, an N channel MOSFET 14 and a diode 15. A control signal converting circuit section 17 uses a control signal line 18 as the input and consists of a diode 19, an inverting amplifire 20 and a non-inverting amplifier 21 and its output connects to the signal switching circuit section 11. An input/output port of a computer 6 is provided with a transmission terminal 7, a reception terminal 8, a ground terminal 9 and a control terminal 23.
FUJITA NORIO
MORI KEIJIRO
MATSUSHITA ELECTRIC IND CO LTD