Tone detector

Claim 2

A tone detector circuit which comprises: means responsive to an applied signal for generating a pulsating signal having a substantially constant amplitude and being representative of intervals between prescribed amplitude levels of said applied signal, said pulsating signal generating means being selectively disabled in response to a predetermined signal being supplied thereto; means in circuit relationship with said pulsating signal generating means and being responsive to at least one predetermined frequency component of said pulsating signal for generating a pulse signal representative of intervals when the amplitude of said at least one frequency component exceeds a predetermined reference level; means for detecting a predetermined amplitude characteristic of said applied signal; and means in circuit relationship with said amplitude detecting means and said pulsating signal generating means and being responsive to the output from saiD amplitude detecting means for generating a signal to disable said pulsating signal generating means during intervals when the output from said amplitude detecting means is below a predetermined level.

Claim 3

A tone detector as defined in claim 1 wherein said amplitude detecting means includes means for generating a signal representative of the average amplitude of said applied signal.

Claim 4

A tone detector as defined in claim 1 wherein said pulsating signal generating means includes a threshold detector for generating a pulsating signal having a substantially constant amplitude and being representative of intervals between prescribed values of the instantaneous amplitude of said applied signal.

Claim 5

A tone detector as defined in claim 3 wherein said pulse signal generating means includes filter means in circuit relationship with said threshold detector for passing only said at least one frequency component of said pulsating signal and level detector means in circuit with said filter means for generating said pulse signal during intervals in which the amplitude of said at least one frequency component exceeds a predetermined level.

Claim 6

A tone detector as defined in claim 4 wherein said level detector means includes peak detector means in circuit with said filter means for generating a unipolarity signal having an amplitude proportional to the peak amplitude value of said at least one frequency component output from said filter means and comparator means having first and second inputs and an output, a reference signal source being connected in circuit with said first input, said peak detector means being connected in circuit with said second input and said comparator means being responsive to a reference signal and to said unipolarity signal for generating said pulse signal at said comparator means output during intervals in which the amplitude of said unipolarity signal exceeds the amplitude of said reference signal.

Claim 7

A tone detector as defined in claim 3 further including interval detector means in circuit relationship with said threshold detector and being responsive to said pulsating signal for generating a predetermined signal only during intervals in which the duration of said pulsating signal exceeds a prescribed interval and at least one means in circuit with said interval detector means and said pulse signal generating means and being responsive to said pulse signal and said interval detector means output for generating an output only during intervals in which said pulse signal and said interval detector means output are in coincidence.

Claim 8

A tone detector as defined in claim 6 wherein said interval detector means includes a retriggerable monostable multivibrator connected in circuit with said threshold detector and having a predetermined unstable interval and means connected in circuit with said multivibrator and being responsive to an output signal from said multivibrator for generating a predetermined signal during intervals in which the output of said multivibrator remains in a predetermined state for a duration greater than a prescribed interval.

Claim 9

A tone detector circuit which comprises: a threshold detector responsive to an applied signal having an amplitude greater than a predetermined level for generating a substantially constant amplitude pulsating signal representative of intervals between prescribed levels of the instantaneous amplitude of said applied signal; means for detecting a prescribed amplitude characteristic of said applied signal; means connected in circuit relationship with said amplitude detecting means and said threshold detector and being responsive to the output from said amplitude detecting means for generating signals to enable and disable said threshold detector during intervals when the output from said amplitude detecting means is above and below a prescribed level, respectively; a plurality of filters in circuit with said threshold detector, each of said filters being arranged to pass an indiviDual frequency component of said pulsating signal; a plurality of peak detector means being in one-to-one circuit relationship with said filters for detecting the peak amplitude of the corresponding passed frequency component; and a plurality of comparator means being in one-to-one circuit relationship with said peak detecting means for comparing said detected peak amplitude to a predetermined reference, wherein the frequency component having a peak amplitude greater than said reference represents the fundamental frequency of said applied signal.

Claim 10

A tone detector circuit which comprises: a threshold detector responsive to an applied signal having an amplitude greater than a predetermined level for generating a substantially constant amplitude pulsating signal representative of intervals between prescribed levels of the instantaneous amplitude of said applied signal; means for detecting a prescribed amplitude characteristic of said applied signal; means connected in circuit relationship with said amplitude detecting means and said threshold detector and being responsive to the output from said amplitude detecting means for generating signals to enable and disable said threshold detector during intervals when the output from said amplitude detecting means is above and below a prescribed level, respectively; a plurality of filters in circuit with said threshold detector, each of said filters being arranged to pass an indiviDual frequency component of said pulsating signal; a plurality of peak detector means being in one-to-one circuit relationship with said filters for detecting the peak amplitude of the corresponding passed frequency component; and a plurality of comparator means being in one-to-one circuit relationship with said peak detecting means for comparing said detected peak amplitude to a predetermined reference, wherein the frequency component having a peak amplitude greater than said reference represents the fundamental frequency of said applied signal.

Claim 11

A tone detector circuit which comprises: means responsive to an applied signal for generating a pulsating signal having a substantially constant amplitude and being representative of intervals between prescribed amplitude levels of said applied signal, said pulsating signal generating means being selectively enabled and disabled in response to predetermined signals supplied thereto; means in circuit relationship with said pulsating signal generating means and being responsive to at least one predetermined frequency component of said pulsating signal for generating a pulse signal representative of intervals when the amplitude of said at least one frequency component exceeds a predetermined reference level; means for generating a signal representative of the average amplitude value of said applied signal; a reference signal source; and comparator means having first and second inputs and an output, said average amplitude signal generating means being in circuit with said first input, said reference signal source being in circuit with said second input, said output being in circuit with said pulsating signal generating means and said comparator means being responsive to signals supplied to said first and second inputs for generating first and second predetermined signals at said output representative of intervals during which the average amplitude of said applied signal is above and below the amplitude of a signal supplied from said reference source, respectively, said first and second predetermined signals being supplied to enable and disable, respectively, said pulsating signal generating means.

Claim 12

A tone detector circuit which comprises: means responsive to an applied signal for generating a pulsating signal having a substantially constant amplitude and being representative of intervals between prescribed amplitude levels of said applied signal, said pulsating signal generating means being selectively enabled and disabled in response to predetermined signals supplied thereto; means in circuit relationship with said pulsating signal generating means and being responsive to at least one predetermined frequency component of said pulsating signal for generating a pulse signal representative of intervals when the amplitude of said at least one frequency component exceeds a predetermined reference level; means for generating a signal representative of the average amplitude value of said applied signal; a reference signal source; and comparator means having first and second inputs and an output, said average amplitude signal generating means being in circuit with said first input, said reference signal source being in circuit with said second input, said output being in circuit with said pulsating signal generating means and said comparator means being responsive to signals supplied to said first and second inputs for generating first and second predetermined signals at said output representative of intervals during which the average amplitude of said applied signal is above and below the amplitude of a signal supplied from said reference source, respectively, said first and second predetermined signals being supplied to enable and disable, respectively, said pulsating signal generating means.

Claim 13

A tone detector circuit which comprises: a threshold detector responsive to an applied signal for generating a pulsating signal having a first polarity during intervals between the instantaneous amplitude of said applied signal exceeding a prescribed level of a first polarity and exceeding a prescribed level of a second polarity and having a second polarity during intervals between the instantaneous amplitude of said applied signal exceeding said prescribed level of said second polarity and exceeding said prescribed level of said first polarity; means for generating a signal representative of the average amplitude value of said applied signal; means in circuit with said average signal generating means and said threshold detector and being responsive to the output from said average signal generating means to generate a signal for disabling said threshold detector during intervals in which the average amplitude of said applied signal is below a prescribed value; a plurality of filters in circuit with said threshold detector, each of said filters being arranged to pass an individual frequency component of said pulsating signal; a plurality of peak detector means in one-to-one circuit relationship with said filters for detecting the peak amplitude of the corresponding frequency component passed by said related filter; and a plurality of comparator means being in one-to-one circuit relationship with said peak detecting means for comparing said detected peak amplitude to a predetermined reference, wherein the frequency component having a peak amplitude greater than said reference represents the fundamental frequency of said applied signal.

Claim 14

A tone detector circuit which comprises: a threshold detector responsive to an applied signal for generating a pulsating signal having a first polarity during intervals between the instantaneous amplitude of said applied signal exceeding a prescribed level of a first polarity and exceeding a prescribed level of a second polarity and having a second polarity during intervals between the instantaneous amplitude of said applied signal exceeding said prescribed level of said second polarity and exceeding said prescribed level of said first polarity; means for generating a signal representative of the average amplitude value of said applied signal; means in circuit with said average signal generating means and said threshold detector and being responsive to the output from said average signal generating means to generate a signal for disabling said threshold detector during intervals in which the average amplitude of said applied signal is below a prescribed value; a plurality of filters in circuit with said threshold detector, each of said filters being arranged to pass an individual frequency component of said pulsating signal; a plurality of peak detector means in one-to-one circuit relationship with said filters for detecting the peak amplitude of the corresponding frequency component passed by said related filter; and a plurality of comparator means being in one-to-one circuit relationship with said peak detecting means for comparing said detected peak amplitude to a predetermined reference, wherein the frequency component having a peak amplitude greater than said reference represents the fundamental frequency of said applied signal.

Claim 15

A tone detector circuit as defined in claim 10 further including interval detecting means connected in circuit with said Threshold detector and being responsive to said pulsating signal for generating a predetermined signal only during intervals in which the interval between pulses of said pulsating signal is less than a predetermined value and in which the duration of said pulsating signal exceeds a predetermined value, a plurality of coincidence gates in one-to-one circuit relationship with the outputs of said plurality of comparing means and in circuit relationship with said interval detecting means, said gates being responsive to generate a predetermined output signal only when the outputs from said comparing means and said interval detecting means are in coincidence.