Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Frequency of cyclic current or voltage
Patent
1974-08-15
1976-04-06
Claffy, Kathleen H.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Frequency of cyclic current or voltage
324 78D, H04M 150, H04Q 146
Patent
active
039491773
ABSTRACT:
Selective digital signal receiver wherein the time distances between zero crossings of the input voltage are measured with a counter controlled at a clock frequency which is high compared with the signal frequency. The main check, covering a plurality of cycles and a predetermined bandwith, is always preceded by a pre-check, covering few cycles and a larger bandwidth. This allows early recognition of push-button dial signals.
REFERENCES:
patent: 3537001 (1970-10-01), Friend
patent: 3790720 (1974-02-01), Schartmann
International Switching Symposium Record, June 1972, pp. 434-441, "Digital Multifrequency Tone Receiver" by S. G. Pitroda.
Ball Herbert
Ohl Wolf
Claffy Kathleen H.
International Standard Electric Corporation
Popek Joseph
Raden J. B.
Warner D. P.
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