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US 4,066,846 AGranted
Combined rotary dial and touch-tone telephone decoding system
AssigneeMelco Inc.
InventorsLouis W. Champan, Arthur T. Perkins
Life of this patent
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AssigneeMelco Inc.
InventorsLouis W. Champan, Arthur T. Perkins
Estimating the term…
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.
In a telephone dialing system, an input line subject to voltage level changes including on-hook, dial pulsing, and completion of a dial pulse sequence, means to differentiate among said voltage level changes comprising a source of clock pulses, means to interpret the voltage level changes in terms of the number of clock pulses by counting the clock pulses in the respective changes and to generate output logic signals indicative of on-hook, off-hook, dial pulses and completion of a dial pulse sequence, and including means to sense a dial pulse when the off-hook signal in the input line goes low for at least a predetermined lower threshold time and no longer than a predetermined upper threshold time, according to the count of said clock pulses, and means to generate an output code of binary signals in accordance with the number of sensed dial pulses, said output code representing the digit dialed.
In a telephone dialing system, an input line adapted to receive Touch-Tone dialing signals and rotary dialing signals, Touch-Tone decoding means connected to said input line and comprising means to derive binary code words representing Touch-Tone frequencies corresponding to Touch-Tone dialed numbers, latched storage means to receive and store the binary code words, means responsive to rotary dial pulses in said input line to generate an output code of binary signals compatible with said first-named binary code words, said output code representing a rotary dialed digit, and means to selectively connect said rotary dialed digit output code generating means and said Touch-Tone decoding means to said latched storage means in accordance with the presence or absence of rotary dial pulses in said input line, wherein said selective connecting means comprises multiplex circuit means normally connecting said Touch-Tone decoding means to said latched storage means, and means to disconnect said Touch-Tone decoding means from said latched storage means and connect said rotary dialed digit output code generating means to said latched storage means responsive to the presence of a valid rotary dialed pulse in said input line.
In a telephone dialing system, an input line adapted to receive Touch-Tone dialing signals and rotary dialing signals, Touch-Tone decoding means connected to said input line and comprising means to derive binary code words representing Touch-Tone frequencies corresponding to Touch-Tone dialed numbers, latched storage means to receive and store the binary code words, said input line being subject to voltage level changes including on-hook, off-hook, dial pulsing, and completion of a dial sequence, means to differentiate among said voltage level changes comprising a source of clock pulses, means to interpret the voltage level changes in terms of the number of clock pulses by counting the clock pulses in the respective changes and including means to sense a valid dial pulse when the off-hook signal in the input line goes low for at least a predetermined lower threshold time and no longer than a predetermined upper threshold time, according to the count of the clock pulses, means to generate an output code of binary signals compatible with said first-named binary code words, according to the count of said clock pulses, said output code representing a rotary dialed digit, and means to selectively connect said rotary dialed digit output code generating means and said Touch-Tone decoding means to said latched storage means in accordance with the sensing of a valid rotary dial pulse.
Dependencies are inferred from the claim text.