| 摘要 |
1,114,983. Signalling over power circuits. ZELLWEGER Ltd. USTER FACTORIES FOR APPARATUS & MACHINES. 4 July, 1966 [4 Aug., 1965], No. 29946/66. Heading H4R. In a method of signalling over power supply conductors the frequency of the control signal generated at the transmitter, and the response frequency of the receiver, are both rigidly related to the frequency of the supply carried by the conductors. The transmitter may include an alternator driven by a synchronous motor fed from the supply conductors, while the receiver may include a tuned filter whose resonance frequency is controlled by the power supply frequency via a frequency discriminator, or alternatively a frequency the same as, or similar to, that generated at the transmitter may be produced from the supply frequency, e.g. by a synchronous oscillator or frequency inverter, to supply a phase-sensitive detector which detects the incoming signalling frequencies. Fig. 1 shows an embodiment of a receiver including a phase-sensitive detector, in which the local oscillation is produced in 18 from the supply conductors 1 and 2. The local oscillation may have exactly the same frequency as the incoming signal in which case the output will depend on the relative phases. Alternatively the frequencies may differ by a known amount to produce at the input of filter 20 the difference frequency which is selected by the low pass or band pass filter 20 and applied via the rectifier bridge 21 to the evaluation relay 22. If the local oscillator frequency is the same as the signalling frequency two phasesensitive detectors may be used fed with phase quadrature local oscillations and the outputs combined to operate the evaluation relay irrespective of the relative phases of the local oscillator and signalling frequency, Fig. 5 (not shown).
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