Combined rotary dial and touch-tone telephone decoding system

Details Combined rotary dial and touch-tone telephone decoding system Combined rotary dial and touch-tone telephone decoding system

1976-08-17

1978-01-03

Claffy, Kathleen H.

179 84VF, H04M 150

Patent

active

040668460

ABSTRACT:
A rotary dial signal processing circuit and an automatic selecting circuit for combining the rotary dial signal processing circuit with a Touch-Tone digital decoding system. The rotary dial signal processing circuit includes means to interpret line signals as to on/off hook condition, dial pulsing, and completion of a dial pulse sequence. This includes estimation of the time durations of specific signal levels. Thus, for a dial pulse the off-hook signal input goes low for 33-90 ms, causing an appropriate system response; there is no system change for a low input signal of less than 25 ms; a low input signal of over 95 ms is interpreted as on-hook, and causes reset; a high input signal of over 150 ms is interpreted as completion of the dial sequence (timeout). The rotary dial signalling processing circuit counts the sensed dial pulses and provides a 4-bit output code which is compatible with the Touch-Tone code. This processing circuit also provides timing signals for the rotary dial/Touch-Tone interface and timeout logic. The rotary dial/Touch-Tone combining circuit buffers key timing outputs of the rotary dial signal processing circuit and renders them compatible with the Touch-Tone counterparts; it also establishes priority as to the rotary dial and Touch-Tone outputs. This circuit multiplexes the rotary dial and Touch-Tone timing signals and also multiplexes the rotary dial signal data and the Touch-Tone data into a common latch device for ultimate transmission to the associated transfer ready group or digit relay tree, as appropriate, and for generation of the ring timeout function.

REFERENCES:
patent: 3538262 (1970-11-01), Gasser et al.
patent: 3851110 (1974-11-01), Kelly et al.
patent: 3917913 (1975-11-01), Patten
patent: 3941937 (1976-03-01), Gauthier
patent: 3941938 (1976-03-01), Gauthier
patent: 4013838 (1977-03-01), Tsai

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