Communications: electrical – Systems – Selsyn type
Patent
1989-08-04
1992-09-01
Ng, Jin F.
Communications: electrical
Systems
Selsyn type
340310R, H04M 1104
Patent
active
051442809
ABSTRACT:
A bidirectional ripple control system in which a code comprises an audio frequency signal superimposed on an electric power distribution system by an LC resonant circuit, controlled by a transmitter crystal oscillator which controls the signal frequency. A receiver has a pair of synchronous filters driven by a receiver crystal oscillator 90 degrees out of phase with each other. The outputs of the filters are squared and summed to form a single output independent of phase. For discrimination the output frequency of each synchronous filter is compared with a set level and the incoming signal is rejected if this frequency exceeds the set level. This system provides a very narrow band frequency detector for the receivers and enables the use of a large number of closely spaced frequencies for the formation of signalling codes. The system provides a means for bidirectional communication on an existing power distribution network.
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Ng Jin F.
The Electricity Trust of South Australia
Tumm Brian R.
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