Multitone pushbutton dial phase shift scanning circuitry

Details Multitone pushbutton dial phase shift scanning circuitry Multitone pushbutton dial phase shift scanning circuitry

1975-07-10

1977-02-08

Miller, Charles D.

Communications: electrical

Audible indication

Percussion-type sound producer

340365C, 179 90K, 328 14, G08C 100

Patent

active

040074595

ABSTRACT:
In a multitone pushbutton dial array each switch in the array has a variable impedance coupling between a fixedly mounted conductive plate and a movable conductive plate spaced apart from the fixedly mounted plate. Digitally synthesized signals having a predetermined phase and frequency are sequentially and recurrently used to scan interconnected columns of movable plates in the pushbutton dial array. Signals having an opposite phase from the scanning signals are continuously applied to the fixedly mounted plates. When a pushbutton is depressed variable impedance coupled summation signals are produced and these signals have a phase which is opposite to that of signals coupled to the detector from an unoperated switch. The detected digital signals are used to generate digital multitone row and column frequency signals. These digital row and column signals are converted to analog form and are transmitted to a telephone central office as a dialed digit code.

REFERENCES:
patent: 3293450 (1966-12-01), Chalfin
patent: 3483553 (1969-12-01), Blankenbaker
patent: 3721976 (1973-03-01), Kuijsten
patent: 3820028 (1974-06-01), Thomas
patent: 3904887 (1975-09-01), Hagelbarger

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