US3934097A — Multifrequency tone detection

Claim 1

Independent Claim 130 words

In a multifrequency tone receiver capable of detecting in a received signal any one of m different tones each a superposition of n component signals having different frequencies, the method of detecting said tones comprising the steps of: taking a sample of said received signal at some arbitrary starting time and at subsequent sampling times delayed therefrom by half-periods and combinations of half-periods of different ones of said commponent signals, performing m independent summations each summation associated with a different one of said tones, and including the starting time sample and 2 n -1 additional samples delayed therefrom by half-periods and combinations of half-periods of the frequencies comprising the corresponding tone, the one summation having approximately zero value corresponding to the one of said tones present in the received signal.

Claim 2

Dependent Claim 130 words

In a multifrequency tone receiver capable of detecting in a received signal any one of m different tones each a superposition of n component signals having different frequencies, the method of detecting said tones comprising the steps of: taking a sample of said received signal at some arbitrary starting time and at subsequent sampling times delayed therefrom by half-periods and combinations of half-periods of different ones of said commponent signals, performing m independent summations each summation associated with a different one of said tones, and including the starting time sample and 2 n -1 additional samples delayed therefrom by half-periods and combinations of half-periods of the frequencies comprising the corresponding tone, the one summation having approximately zero value corresponding to the one of said tones present in the received signal.

Claim 3

Dependent Claim 21 words

The method of claim 1 in which said performing step comprises, for each summation: sequentially accumulating the samples of such summation.

Claim 4

Dependent Claim 39 words

The method of claim 1 in which said performing step comprises: independently storing each one of said samples and adding all the samples required for each one of said summations upon receipt of the last sample for that summation.

Claim 5

Dependent Claim 231 words

In a multifrequency tone detector including a plurality of storage capacitors the method of detecting the presence in a received signal of any one of m tones, each tone being a superposition of n component signals having different frequencies, comprising the steps of: taking a sample of said received signal at an arbitrary starting time and at subsequent times delayed therefrom by half-periods and combinations of half-periods of different ones of said component signals, storing, in different ones of said storage capacitors, said starting time sample and each subsequent sample delayed therefrom by a combination of less than n ones of said half-periods, at each final sampling time delayed from said starting time sample by a combination of n of said half-periods, connecting in series a subgroup of said capacitors and transmitting through said subgroup the sample taken at said final sampling time, said subgroup comprising those capacitors storing the starting time sample and samples delayed therefrom by subcombinations of the half-periods constituting the delay of said final sampling time, sensing the amplitude of the signal transmitted through said capacitor subgroup at each final sampling time, and indicating when the summation of samples of one of said tones has approximately zero amplitude thereby detecting the presence of a tone whose component half-periods constitute the delay, from said starting time sample, of the final sampling time at which said zero value occurred.

Claim 6

Dependent Claim 231 words

In a multifrequency tone detector including a plurality of storage capacitors the method of detecting the presence in a received signal of any one of m tones, each tone being a superposition of n component signals having different frequencies, comprising the steps of: taking a sample of said received signal at an arbitrary starting time and at subsequent times delayed therefrom by half-periods and combinations of half-periods of different ones of said component signals, storing, in different ones of said storage capacitors, said starting time sample and each subsequent sample delayed therefrom by a combination of less than n ones of said half-periods, at each final sampling time delayed from said starting time sample by a combination of n of said half-periods, connecting in series a subgroup of said capacitors and transmitting through said subgroup the sample taken at said final sampling time, said subgroup comprising those capacitors storing the starting time sample and samples delayed therefrom by subcombinations of the half-periods constituting the delay of said final sampling time, sensing the amplitude of the signal transmitted through said capacitor subgroup at each final sampling time, and indicating when the summation of samples of one of said tones has approximately zero amplitude thereby detecting the presence of a tone whose component half-periods constitute the delay, from said starting time sample, of the final sampling time at which said zero value occurred.

Claim 7

Dependent Claim 101 words

In an apparatus capable of detecting the presence in a received signal of any one of m tones each including m different component frequencies, the combination of: means for taking a sample of said received signal at some arbitrary starting time and at subsequent times delayed therefrom by half-periods and combinations of half-periods of different ones of said component frequencies and, means for independently combining the samples corresponding to each of said m tones, the samples corresponding to a particular tone being the starting time sample plus those delayed therefrom by half-periods and combinations of half-periods of that tone's component frequencies.

Claim 8

Dependent Claim 101 words

In an apparatus capable of detecting the presence in a received signal of any one of m tones each including m different component frequencies, the combination of: means for taking a sample of said received signal at some arbitrary starting time and at subsequent times delayed therefrom by half-periods and combinations of half-periods of different ones of said component frequencies and, means for independently combining the samples corresponding to each of said m tones, the samples corresponding to a particular tone being the starting time sample plus those delayed therefrom by half-periods and combinations of half-periods of that tone's component frequencies.

Claim 9

Independent Claim 159 words

An apparatus, responsive to a periodic sequence of clock pulses, for detecting in a received signal the presence of any of m tones, each tone being a superposition of n different component frequencies, said apparatus comprising: means responsive to said clock pulses for generating first, second and third control signals, means enabled by said first control signal for taking a sample of said received signal at some arbitrary starting time and at subsequent times delayed therefrom by half-periods and combinations of half-periods of different ones of said component frequencies, means responsive to said second control signal for independently combining the samples corresponding to each of said m tones, the samples corresponding to a particular tone being the starting time sample plus those delayed therefrom by half-periods and combinations of different half-periods of that tone's component frequencies, and means enabled by said third control signal for indicating when sample combinations produced by said combining means achieve an approximately zero value.

Claim 10

Independent Claim 159 words

An apparatus, responsive to a periodic sequence of clock pulses, for detecting in a received signal the presence of any of m tones, each tone being a superposition of n different component frequencies, said apparatus comprising: means responsive to said clock pulses for generating first, second and third control signals, means enabled by said first control signal for taking a sample of said received signal at some arbitrary starting time and at subsequent times delayed therefrom by half-periods and combinations of half-periods of different ones of said component frequencies, means responsive to said second control signal for independently combining the samples corresponding to each of said m tones, the samples corresponding to a particular tone being the starting time sample plus those delayed therefrom by half-periods and combinations of different half-periods of that tone's component frequencies, and means enabled by said third control signal for indicating when sample combinations produced by said combining means achieve an approximately zero value.

Claim 11

Dependent Claim 142 words

The apparatus of claim 6 in which said generating means comprises: a sample pulse counter responsive to transitions in said first control signal said sample pulse counter having a maximum enumeration coextensive with the total number of said samples taken in performing a detection, a clock pulse counter, resettable by pulses in said first control signal, said clock pulse counter having a maximum enumeration of m+1, means jointly responsive to the enumerations of said sample pulse counter and said clock pulse counter to produce a delay count, said second control signal and said third control signal, and variable delay means jointly responsive to said clock pulses and pulses in said first control signal for delaying pulses in said first control signal by the number of clock pulse periods determined by said delay count to produce subsequent pulses in said first control signal.

Claim 12

Dependent Claim 66 words

The generating means of claim 7 in which said variable delay means comprises: means settable to said delay count upon the occurrence of a transition of a pulse in said first control signal for counting said clock pulses, and means responsive to a predetermined enumeration of said settable counting means to produce a pulse coincident therewith, the sequence of such pulses comprising said first control signal.

Claim 13

Dependent Claim 110 words

The apparatus of claim 6 in which said generating means comprises: a sample pulse counter responsive to transitions in said first control signal having a maximum enumeration coextensive with the total number of said samples taken in performing a detection, means responsive to the enumeration of said sample pulse counter to produce a delay count, said second control signal and said third control signal, and variable delay means jointly responsive to said clock pulses and pulses in said first control signal for delaying pulses in said first control signal by the number of clock pulse periods determined by said delay count to produce subsequent pulses in said first control signal.

Claim 14

Dependent Claim 66 words

The generating means of claim 9 in which said variable delay means comprises: means settable to said delay count upon the occurrence of a transition of a pulse in said first control signal for counting said clock pulses, and means responsive to a predetermined enumeration of said settable counting means to produce a pulse coincident therewith, the sequence of such pulses comprising said first control signal.

Claim 15

Dependent Claim 75 words

The apparatus of claim 6 in which said generating means comprises: means for counting said clock pulses having a maximum enumeration which occurs within a predetermined time allotted for detecting a tone, said maximum enumeration being sufficiently large for said counting means to produce different enumerations during respective instants when said samples are taken, and count decoding means responsive to the enumeration of said counting means to provide said first, second and third control signals.

Claim 16

Dependent Claim 52 words

The apparatus of claim 6 in which said sample-taking means comprises: an analog-to-digital converter responsive to said received signal for providing a plurality of output bits representative of the amplitude of said recevied signal, and a register responsive to said first control signal for storing the output bits of said analog-to-digital converter.

Claim 17

Dependent Claim 93 words

The apparatus of claim 6 in which said combining means comprises: means for adding each of said samples to accumulations of preceding samples, to produce updated accumulations, and segmented means responsive to second control signal for storing updated accumulations produced by said adding means, said stored updated accumulations being provided as the accumulation of preceding samples to said adding means, each segment of said storage means being dedicated to a unique one of said m tones, and the segment addressed at any instant being determined by the value of said second control signal.

Claim 18

Dependent Claim 74 words

The apparatus of claim 6 in which said combining means comprises: segmented means responsive to said second control signal for storing each of said samples in a unique segment and for simultaneously reading out the contents of 2 n segments, the particular segments stored in and read out at any instant being determined by the value of said second control signal, and means for adding the contents read out from said 2 n segments.

Claim 19

Independent Claim 331 words

An apparatus for detecting the presence in a received signal of any one of a plurality of multifrequency tones comprising: means for generating a plurality of control signals, an input terminal to which said received signal is applied, a common terminal connected to ground potential, a first storage capacitor, first and second capacitor switches responsive to a unique one of said control signals for connecting, respectively, a first terminal of said capacitor to said input terminal and the second terminal of said capacitor to said common terminal, a mode switch responsive to a unique one of said control signals and having two connection terminals to provide a continuity connection therebetween, one of said connection terminals being connected to said input terminal, a plurality of two terminal storage networks serially connected between the second terminal of said storage capacitor and the free terminal of said mode switch, each of said networks comprising: a plurality of storage capacitors connected at one end to the same storage network terminal, a plurality of switches each responsive to a unique one of said control signals for providing a connection between the free end of one of said capacitors and the free one of said storage network terminals, a plurality of network switch pairs, each pair responsive to a unique one of said control signals and dedicated to one of said storage networks, one switch in each pair providing a connection between a first terminal of the corresponding storage network and said input terminal, the remaining switch in each pair providing a connection between the second terminal of the corresponding storage network and said common terminal, a null detector having an input terminal and an output terminal, said detector indicating at its output terminal when a signal applied at its input terminal exceeds some predetermined value, and an output switch responsive to a unique one of said control signals to connect the first terminal of said first storage capacitor to the input terminal of said threshold detector.

Claim 20

Independent Claim 331 words

An apparatus for detecting the presence in a received signal of any one of a plurality of multifrequency tones comprising: means for generating a plurality of control signals, an input terminal to which said received signal is applied, a common terminal connected to ground potential, a first storage capacitor, first and second capacitor switches responsive to a unique one of said control signals for connecting, respectively, a first terminal of said capacitor to said input terminal and the second terminal of said capacitor to said common terminal, a mode switch responsive to a unique one of said control signals and having two connection terminals to provide a continuity connection therebetween, one of said connection terminals being connected to said input terminal, a plurality of two terminal storage networks serially connected between the second terminal of said storage capacitor and the free terminal of said mode switch, each of said networks comprising: a plurality of storage capacitors connected at one end to the same storage network terminal, a plurality of switches each responsive to a unique one of said control signals for providing a connection between the free end of one of said capacitors and the free one of said storage network terminals, a plurality of network switch pairs, each pair responsive to a unique one of said control signals and dedicated to one of said storage networks, one switch in each pair providing a connection between a first terminal of the corresponding storage network and said input terminal, the remaining switch in each pair providing a connection between the second terminal of the corresponding storage network and said common terminal, a null detector having an input terminal and an output terminal, said detector indicating at its output terminal when a signal applied at its input terminal exceeds some predetermined value, and an output switch responsive to a unique one of said control signals to connect the first terminal of said first storage capacitor to the input terminal of said threshold detector.

Claim 21

Dependent Claim 36 words

The combination of claim 5 further comprising means for detecting when the combination of samples corresponding to any of said tones has approximately zero value thereby indicating the presence of such tone in said received signal.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1979-01-19	1979-07-21	1980-01-20	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1983-01-19	1983-07-21	1984-01-20	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1987-01-19	1987-07-21	1988-01-20	$7700.00	Window Closed / Lapsed

Multifrequency tone detection

Abstract

Inventors

Bibliographic Details

Claims Analysis

References Cited (Backward Citations)

USPTO Annuity & Maintenance Windows

Assigned Categories & Tags

Assign Category Tag