| 摘要 |
Remote control signals which are transmitted non-line-conducted by means of radio-frequency waves are used for switching load objects on and off in a power system. For this purpose, radio waves of existing transmitters, for example broadcast transmitters operating in the medium-wave band (520-1560 kHz) can be used. The transmitter operating in amplitude modulation is modulated, also in amplitude modulation, with the remote control commands in a frequency range which is below the ordinary modulation band (10 to 30 Hz with an audio-frequency range from 50 to 10,000 Hz). For this extraordinary modulation, a reduced modulation percentage of 5% is provided so that no special measures need to be provided at the transmitter end. The receiver (1) for these remote control commands is designed in such a manner that it is capable of separating the weakly modulated pulses from the ordinary modulation so that the latter cannot trigger any faulty switching. For this reason, a low-frequency filter (12) is provided as essential component of the receiver in order to recover the coded remote control commands. The output of the filter (12) is conducted via a rectifier (15) to a level comparator (18) which only passes pulse sequences which reach a modulation percentage of approximately 5%. The switching member (2) for switching a load object (3) on or off is controlled via a following decoder (21). <IMAGE> |
