| 摘要 |
<p>The system which allows simultaneous transmission of up to 20 instructions uses 100% amplitude modulation of an infrared beam. Modulation is effected by a carrier frequency of several tens or hundreds of kilohertz. This carrier signal is itself modulated by a train of coded pulses carrying the information to be transmitted. The infrared transmitter uses light emitting diodes controlled from a fixed of movable control panel. A metal receiving box containing one or more photodiodes detects the IR signal, and includes a low noise preamplifier operating at the transmission carrier frequency. This signal is then transmitted at low impedance via a coaxial cable to the receiver itself. This strongly amplifies the signal, and after demodulation recovers the control pulse signals.</p> |
