Tone phase shift detector

Details Tone phase shift detector Tone phase shift detector

1977-11-23

1979-10-16

Bookbinder, Marc E.

Electricity: measuring and testing

Measuring, testing, or sensing electricity, per se

Frequency of cyclic current or voltage

324 83D, 325478, 328155, H04B 116

Patent

active

041715160

ABSTRACT:
The prior art tone detector shown in U.S. Pat. No. 3,962,645 provides a repetitive sequence of vector signals at a predetermined or selected rate determined by the desired tone frequency to be detected. Each vector in the sequence has a different phase or angular direction. One vector in each sequence is selected at a time corresponding to a selected (usually zero) point in each cycle of received tone frequency. If the sum of a number of selected vectors exceeds a threshold, an indication of the desired tone is provided.
In some tone detectors a phase shift in the tone can indicate a selected condition. Such a phase shift is detected by counting the number of vectors which are produced after the phase shift, whose magnitude added to the magnitude of the vectors produced before the phase shift exceeds a threshold, and whose sign differs from the sign of the vectors produced before the phase shift. When the count reaches a predetermined number, a phase shift indication is provided.

REFERENCES:
patent: 3683345 (1972-08-01), Faulkes et al.
patent: 3949301 (1976-04-01), Mattei
patent: 3962645 (1976-08-01), Stewart

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