Electricity: electrical systems and devices – Control circuits for electromagnetic devices – For relays or solenoids
Patent
1975-03-27
1977-03-08
Moose, Harry
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
For relays or solenoids
307129, 340171R, H01H 4720
Patent
active
040114864
ABSTRACT:
Disclosed is a switching arrangement operable by a tone of a predetermined frequency. An automatic gain control amplifier has an input connectable to a source of signals and an output connected to an input of a bandpass filter which rejects all frequencies except those of a narrow band centered on the predetermined frequency. The bandpass filter is connected to an input of a phase locked loop which produces a change in voltage from a first level to a second level at its output only in response to a narrow band of frequencies centered on the predetermined frequency. The output of the phase locked loop is connected to a timer which only produces a pulse at its output upon receipt of the second level of voltage for a predetermined time. A pulse from the timer is fed to a flip-flop which changes state and operates a relay. The arrangement is particularly useful in a loop-back unit whereby equipment may be disconnected from a receive line and a transmit line and the two lines connected together for testing purposes.
REFERENCES:
patent: 3440347 (1969-04-01), Spencer et al.
patent: 3651474 (1972-03-01), Liberman
patent: 3784848 (1974-01-01), Hamilton
patent: 3835454 (1974-09-01), Palmieri et al.
Moose Harry
Pylon Electronic Development Company Ltd.
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