| 摘要 |
The circuit has a conventional infrared-emitting diode (5) with its anode connected to the output port (7) of a programmable microprocessor (9) for half-duplex asynchronous serial bit data transmission to a distant equipment (3). The cathode is connected by resistances (11,15) to a DC supply point (13) and to a tri-state buffer bidirectional data transmission port (17). The same diode serves as a photodetector for the returning optical signal, being biased against conduction so as to detect a voltage which is dependent on its blocking current and the intensity of illumination. In a particular embodiment it functions also as a sensor for the operation of an optical key. |
