Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Frequency of cyclic current or voltage
Patent
1977-04-28
1979-01-02
Robinson, Thomas A.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Frequency of cyclic current or voltage
324186, H04M 322, G04F 900
Patent
active
041328647
ABSTRACT:
The duty cycle of an AC telephone off-hook signal is measured by means of comparing it with the duty cycle of a known AC signal having a duty cycle of 0.5 because it has a DC component of zero. Measurement of the duty cycle in a telephone off-hook detector application involves measuring the DC portion of the signal on a pair of telephone lines from a telephone handset to an exchange. A high frequency master clock oscillator with a much higher frequency than the basic ringing voltage is used. An input signal is used to gate clock pulses to a counter when the input signal is positive. At the end of a predetermined number of clock pulses, the counter is gated into memory connected to a decoder for transmission of the decoded signal to the exchange for appropriate action.
REFERENCES:
patent: 3735263 (1973-05-01), Boatwright
patent: 3851108 (1974-11-01), Freimanis
International Business Machines - Corporation
Jones II Graham S.
Robinson Thomas A.
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