Multifrequency sequential tone decoder

Claim 2

A multifrequency sequential tone decoder adapted to be responsive to an inpuT tone signal, comprising: a. a frequency responsive bandpass filter adapted to be selectively responsive to an individual one of a plurality of frequencies, said frequency responsive bandpass filter including output means for providing a logic level output in response to an input tone signal of said selected frequency; b. sample position means responsive to said logic level output for providing a first test pulse after a predetermined period of time; c. tone timing means 26 responsive to said logic level output for providing a reset signal when said logic level output fails to persist a predetermined period of time; d. silence position means for providing after a predetermined period of time after the termination of said first test pulse a second test pulse; e. silence timing means for providing a reset signal when said input tone signal exceeds a predetermined amplitude after a predetermined period of time measured from the termination of said first test pulse; and f. counter means operative in a first mode upon sequential termination of said first and second test pulses for effecting the switching of said frequency responsive bandpass filter to a second one of said plurality of frequencies and in a second mode in response to any one of said reset signals for switching said frequency responsive bandpass filter to a first one of said plurality of frequencies.

Claim 3

A multifrequency sequential tone decoder as defined in claim 1, further comprising: a decoder responsive to said counter means reaching a predetermined count for providing an output signal.

Claim 4

A multifrequency sequential tone decoder as defined in claim 2, further comprising: an end of code timer for providing a reset signal when said counter fails to reach a predetermined count within a predetermined period of time.

Claim 5

A multifrequency sequential tone decoder as defined in claim 3, further comprising: a code selector disposed between said counter and said frequency responsive bandpass filter for controlling the sequence of selection of the responsive frequencies of said frequency responsive bandpass filters.

Claim 6

A multifrequency sequential tone decoder adapted to be responsive to an input tone signal, comprising: a plurality of frequency responsive bandpass filters adapted to be selectively responsive to individual ones of a plurality of frequencies, said frequency responsive bandpass filters including output means for providing logic level outputs in response to an input tone signal of said selected frequency; b. sample position means responsive to said logic level output for providing a first test pulse after a predetermined period of time; c. tone detector means responsive to said logic level output for providing a reset signal when said logic level output fails to persist a predetermined period of time; d. silence position means for providing a second test pulse after a predetermined period of time after the termination of said first test pulse; e. silence detector means for providing a reset signal when said input tone signal exceeds a predetermined amplitude after a predetermined period of time measured from the termination of said first test pulse; and f. counter means operative in a first mode upon sequential termination of said first and second test pulses for switching said frequency responsive bandpass filters to second ones of said plurality of frequencies, and in a second mode in response to said reset signals for switching said frequency responsive bandpass filters to first ones of said plurality of frequencies.

Claim 7

A multifrequency sequential tone decoder adapted to be responsive to an input tone signal, comprising: a plurality of frequency responsive bandpass filters adapted to be selectively responsive to individual ones of a plurality of frequencies, said frequency responsive bandpass filters including output means for providing logic level outputs in response to an input tone signal of said selected frequency; b. sample position means responsive to said logic level output for providing a first test pulse after a predetermined period of time; c. tone detector means responsive to said logic level output for providing a reset signal when said logic level output fails to persist a predetermined period of time; d. silence position means for providing a second test pulse after a predetermined period of time after the termination of said first test pulse; e. silence detector means for providing a reset signal when said input tone signal exceeds a predetermined amplitude after a predetermined period of time measured from the termination of said first test pulse; and f. counter means operative in a first mode upon sequential termination of said first and second test pulses for switching said frequency responsive bandpass filters to second ones of said plurality of frequencies, and in a second mode in response to said reset signals for switching said frequency responsive bandpass filters to first ones of said plurality of frequencies.

Claim 8

A multifrequency sequential tone decoder as defined in claim 5, further comprising: a detector responsive to said logic level output for inhibiting the operation of all of said frequency responsive bandpass filters except said frequency responsive bandpass filter which generated said logic level output, and responsive to the termination of said second test pulse for uninhibiting all of said frequenCy responsive bandpass filters.

Claim 9

A multifrequency sequential tone decoder as defined in claim 6, further comprising: a decoder responsive to said means reaching a predetermined count for providing an output signal.

Claim 10

A multifrequency sequentail tone decoder as defined in claim 7, further comprising: an end of code timer for providing upon termination of said second test pulse a reset signal when said counter means fails to reach a predetermined count within a predetermined period of time.

Claim 11

A multifrequency sequential tone decoder as defined in claim 8, further comprising: code selectors disposed between said counter means and said frequency responsive bandpass filters for controlling the sequence of selection of the responsive frequencies of said frequency responsive bandpass filters.

Claim 12

A multifrequency sequential tone decoder adapted to be responsive to an input tone signal, comprising: A. a plurality of frequency responsive bandpass filters adapted to be selectively responsive to individual ones of a plurality of frequencies, said frequency responsive bandpass filters including output means for providing logic level outputs in response to an input of said selected frequency; b. detector means responsive to said logic level output for inhibiting the operation of all of said frequency responsive bandpass filters except said frequency responsive bandpass filter which generated said logic level output; c. sample position means responsive to said logic level output for providing a first test pulse after a predetermined period of time; d. tone detector means responsive to said logic level output for providing a reset signal when said logic level output fails to persist until the termination of said first test pulse; e. silence position means for providing a second test pulse after a predetermined period of time measured from the termination of said first test pulse; f. silence detector means for providing a reset signal when said input tone signal exceeds a predetermined amplitude after a predetermined period of time measured from the termination of said first test pulse; g. a counter means operative in a first mode upon sequential termination of said first and second test pulses for providing in sequence a plurality of coded outputs, and in a second mode for providing the first coded output of said plurality in response to said reset signal; h. code selectors responsive to said plurality of coded outputs for switching said frequency responsive bandpass filters to predetermined ones of said plurality of frequencies; i. decoder means responsive to said counter reaching a predetermined count for providing an output signal; j. said counter means responsive to said reset signal for actuating said detector to uninhibit the operation of all of said inhibited frequency responsive bandpass filters; and k. an end of code timer for providing upon the occurrence of the termination of said second test pulse a reset signal when said counter means fails to reach a predetermined count within a predetermined period of time.

Claim 13

A multifrequency sequential tone decoder adapted to be responsive to an input tone signal, comprising: A. a plurality of frequency responsive bandpass filters adapted to be selectively responsive to individual ones of a plurality of frequencies, said frequency responsive bandpass filters including output means for providing logic level outputs in response to an input of said selected frequency; b. detector means responsive to said logic level output for inhibiting the operation of all of said frequency responsive bandpass filters except said frequency responsive bandpass filter which generated said logic level output; c. sample position means responsive to said logic level output for providing a first test pulse after a predetermined period of time; d. tone detector means responsive to said logic level output for providing a reset signal when said logic level output fails to persist until the termination of said first test pulse; e. silence position means for providing a second test pulse after a predetermined period of time measured from the termination of said first test pulse; f. silence detector means for providing a reset signal when said input tone signal exceeds a predetermined amplitude after a predetermined period of time measured from the termination of said first test pulse; g. a counter means operative in a first mode upon sequential termination of said first and second test pulses for providing in sequence a plurality of coded outputs, and in a second mode for providing the first coded output of said plurality in response to said reset signal; h. code selectors responsive to said plurality of coded outputs for switching said frequency responsive bandpass filters to predetermined ones of said plurality of frequencies; i. decoder means responsive to said counter reaching a predetermined count for providing an output signal; j. said counter means responsive to said reset signal for actuating said detector to uninhibit the operation of all of said inhibited frequency responsive bandpass filters; and k. an end of code timer for providing upon the occurrence of the termination of said second test pulse a reset signal when said counter means fails to reach a predetermined count within a predetermined period of time.

Claim 14

A multifrequency sequential tone decoder for identifying an input signal having an address portion comprised of a tone burst of selected frequency and first predetermined duration followed by a blank portion of relatively lower amplitude and second predetermined duration, said decoder comprising: a. filter means coupled to receive the input signal and selectively controllable to respond to one of a plurality of frequencies to provide an output signal indicative of the selected one frequency; b. duration timer means for providing a firt output signal corresponding to one of said predetermined durations after the occurrence of the output signal of said filter means; c. burst timing means responsive to the output signals of said duration timer means and said filter means for providing a reset signal if said output of said filter means does not last for the first prEdetermined duration; d. counter means operative in a first mode for effecting the operation of said filter means to be responsive to another one of said plurality of frequencies, and in a second mode in response to the reset signal for effecting the operation of said filter means to be responsive to a first one of said plurality of frequencies; e. said duration timer means for providing a second output signal corresponding to the second duration upon a change of said counter means from its first to its second mode of operation, said counter means responsive to the second output signal of said duration timer means to be disposed in its first mode of operation; and f. blank timing means responsive to the second output signal of said duration timer means for generating a reset signal to be applied to said counter means when the input signal exceeds the relatively low amplitude.

Claim 15

A multifrequency sequential tone decoder for identifying an input signal having an address portion comprised of a tone burst of selected frequency and first predetermined duration followed by a blank portion of relatively lower amplitude and second predetermined duration, said decoder comprising: a. filter means coupled to receive the input signal and selectively controllable to respond to one of a plurality of frequencies to provide an output signal indicative of the selected one frequency; b. duration timer means for providing a firt output signal corresponding to one of said predetermined durations after the occurrence of the output signal of said filter means; c. burst timing means responsive to the output signals of said duration timer means and said filter means for providing a reset signal if said output of said filter means does not last for the first prEdetermined duration; d. counter means operative in a first mode for effecting the operation of said filter means to be responsive to another one of said plurality of frequencies, and in a second mode in response to the reset signal for effecting the operation of said filter means to be responsive to a first one of said plurality of frequencies; e. said duration timer means for providing a second output signal corresponding to the second duration upon a change of said counter means from its first to its second mode of operation, said counter means responsive to the second output signal of said duration timer means to be disposed in its first mode of operation; and f. blank timing means responsive to the second output signal of said duration timer means for generating a reset signal to be applied to said counter means when the input signal exceeds the relatively low amplitude.

Claim 16

The tone decoder as claimed in claim 11, wherein there is further included programmable decoder means responsive to the count output of said counter means for selectively controlling the one frequency to which said filter means is responsive as the count output of said counter means advances in response to the output signals of said duration timer means.

Claim 17

The tone decoder as claimed in claim 11, wherein there is further included at least second filter means selectively controllable to be responsive to one of a plurality of frequencies to provide an output signal indicative of the selected one frequency; and detector means responsive to the output of one of said first-mentioned and second filter means for actuating the other of said filter means to respond to its one frequency and for deactuating said one filter means.

Claim 18

The tone decoder as claimed in claim 11, wherein said burst timing means is deactuated when said counter means is operative in its second mode, and said blank timing means is deactuated when said counter means is operative in its first mode.

Claim 19

The tone decoder as claimed in claim 11, wherein there is further included amplitude detecting means responsive to the input signal for providing an output indicative of an input signal exceeding the relatively lower amplitude, and said blank timing means responsive to the output of said amplitude detecting means and the second output signal of said duration timer means for generating a reset signal.