Multifrequency tone receiver

Claim 2

A receiver for detecting the simultaneous presence in a multifrequency tone signal of a plurality of frequencies assigned to different ones of a plurality of frequency groups comprising a plurality of intragroup frequency detectors for indicating the presence in said input signal of individual frequencies from each of said plurality of frequency groups; at least one intergroup frequency detector for indicating the presence in said input signal of frequencies lying between said frequency groups; and decoding means jointly responsive to said intragroup and intergroup frequency detectors for producing a receiver output when only one frequency is detected in each of said frequency groups and no frequency is detected between said frequency groups.

Claim 3

The receiver of claim 1 in which each one of said intragroup frequency detectors comprises a frequency-to-voltage converter for linearly converting the frequencies from one of said plurality of frequency groups to a voltage amplitude lying in a predetermined amplitude range; a reference source providing a plurality of voltage pairs defining each of said amplitude ranges; and a voltage sensor jointly responsive to said converted voltage amplitude and said reference voltage pairs for indicating which amplitude range bounds said converted voltage amplitude.

Claim 4

The receiver of claim 2 in which said frequency-to-voltage converter comprises a phase-locked loop.

Claim 5

The receiver of claim 1 in which each said intergroup frequency detector comprises a frequency-to-voltage converter for linearly converting intergroup frequencies in said input signal to a voltage amplitude with a predetermined range; a threshold-level source providing at least one reference voltage corresponding to a boundary of an unassigned range of intergroup frequencies; and a voltage sensor jointly responsive to said voltage amplitude and to each reference voltage for indicating when the amplitude of said voltage amplitude falls in an amplitude range bounded by each reference voltage.

Claim 6

The receiver of claim 4 in which the second boundary of said unassigned range of frequencies comprises the limit of the linear region of said frequency-to-voltage converter.

Claim 7

The receiver of claim 4 in which said frequency-to-voltage converter comprises a phase-locked loop.

Claim 8

A receiver for detecting the simultaneous presence in a multifrequency tone signal of a plurality of frequencies assigned to different ones of a plurality of frequency groups comprising a plurality of filters for separating said tone signal into frequency groups; a plurality of intragroup frequency detectors for frequencies lying within each frequency group; at least one intergroup frequency detector for frequencies lying between said frequency groups; and means jointly responsive to said intragroup and intergroup frequency detectors for producing a valid receiver output only when one frequency is detected within each of said frequency groups and no frequency is detected between said frequency groups.

Claim 9

A receiver for detecting the simultaneous presence in a multifrequency tone signal of a plurality of frequencies assigned to different ones of a plurality of frequency groups comprising a plurality of filters for separating said tone signal into frequency groups; a plurality of intragroup frequency detectors for frequencies lying within each frequency group; at least one intergroup frequency detector for frequencies lying between said frequency groups; and means jointly responsive to said intragroup and intergroup frequency detectors for producing a valid receiver output only when one frequency is detected within each of said frequency groups and no frequency is detected between said frequency groups.

Claim 10

The receiver of claim 7 in which each one of said group frequency detectors comprises a frequency-to-voltage converter for linearly converting the tone frequencies from one of said plurality of frequency groups to voltage amplitudes lying in predetermined amplitude ranges; a plurality of pairs of reference voltages defining said amplitude ranges; and a voltage sensor jointly responsive to said converted voltage amplitudes and said pairs of reference voltages for indicating whether said voltage amplitudes lie between or outside said amplitude ranges.

Claim 11

The receiver of claim 8 in which said frequency-to-voltage converter comprises a phase-locked loop.

Claim 12

The receiver of claim 7 in which each one of said intergroup frequency detectors comprises a frequency-to-voltage converter for linearly converting intergroup frequencies in said tone signal to a voltage amplitude in a predetermined ranGe; a threshold-level source providing at least one reference voltage corresponding to a boundary of an unassigned range of intergroup frequencies; and a voltage sensor jointly responsive to said voltage amplitudes and to each reference voltage for indicating when the amplitude of said voltage amplitude falls in an amplitude range bounded by each said reference voltage.

Claim 13

The receiver of claim 10 in which the second boundary of said unassigned range of frequencies comprises the limit of the linear region of said frequency-to-voltage converter.

Claim 14

The receiver of claim 10 in which said frequency-to-voltage converter comprises a phase-locked loop.

Claim 15

In a communications system employing multi-frequency tones, including one frequency from each of a plurality of discrete frequency groups, for end-to-end signaling, a receiver for detecting and identifying each of said tones comprising a plurality of filters for separating said tones into frequency groups; a plurality of intragroup frequency detectors for producing digital signals identifying discrete frequencies within each frequency group, each group frequency detector comprising a phase-locked loop for linearly converting the tone frequencies from one of said frequency groups to voltage amplituds lying in predetermined amplitude ranges, a plurality of pairs of reference voltages defining said amplitude ranges, and a voltage sensor jointly responsive to said converting voltage amplitudes and said pairs of reference voltages for indicating whether said voltage amplitudes lie within or outside said amplitude ranges; at least one intergroup frequency detector for producing digital signals indicating the presence in said input signal of frequencies lying between said frequency groups, each intergroup frequency detector comprising a phase-locked loop for linearly converting intergroup frequencies in said tone signal to a voltage amplitude in a predetermined range, a threshold-level source providing at least one reference voltage corresponding to a boundary of an unassigned range of frequencies, and a voltage sensor jointly responsive to said voltage amplitudes and to each reference voltage for indicating when the amplitude of said voltage amplitude falls in an amplitude range bounded by each reference voltage; and decoding means jointly responsive to digital signals from said intragroup and intergroup frequency detectors for producing a digital output signal representative of the particular tone received when only one frequency is detected in each of said frequency groups and no frequency is detected between said frequency groups.

Claim 16

In a communications system employing multi-frequency tones, including one frequency from each of a plurality of discrete frequency groups, for end-to-end signaling, a receiver for detecting and identifying each of said tones comprising a plurality of filters for separating said tones into frequency groups; a plurality of intragroup frequency detectors for producing digital signals identifying discrete frequencies within each frequency group, each group frequency detector comprising a phase-locked loop for linearly converting the tone frequencies from one of said frequency groups to voltage amplituds lying in predetermined amplitude ranges, a plurality of pairs of reference voltages defining said amplitude ranges, and a voltage sensor jointly responsive to said converting voltage amplitudes and said pairs of reference voltages for indicating whether said voltage amplitudes lie within or outside said amplitude ranges; at least one intergroup frequency detector for producing digital signals indicating the presence in said input signal of frequencies lying between said frequency groups, each intergroup frequency detector comprising a phase-locked loop for linearly converting intergroup frequencies in said tone signal to a voltage amplitude in a predetermined range, a threshold-level source providing at least one reference voltage corresponding to a boundary of an unassigned range of frequencies, and a voltage sensor jointly responsive to said voltage amplitudes and to each reference voltage for indicating when the amplitude of said voltage amplitude falls in an amplitude range bounded by each reference voltage; and decoding means jointly responsive to digital signals from said intragroup and intergroup frequency detectors for producing a digital output signal representative of the particular tone received when only one frequency is detected in each of said frequency groups and no frequency is detected between said frequency groups.

Claim 17

The tone receiver of claim 13 in which the second boundary of the unassigned range of frequencies in each intergroup frequency detector comprises the limit of the linear range of the corresponding phase-locked loop.

Claim 18

The tone receiver of claim 13 which detects and identifies tones including two frequencies comprising two intragroup frequency detectors and a single intergroup frequency detector.