Patent EP0213651A1 successfully refreshed from Google Patents.
EP0213651A1
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Receiving equipment for the recognition of a number of different and predetermined frequency combinations of voice-frequency signalling components under the protection of a spurious-signal/voice-signal guard function
Assignee: Koninklijke Philips NV
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Filing: 1986-07-08
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Granted: —
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Expires: 2006-07-08
Abstract
Abstract Universal signalling receiver containing a speech detector specialty developed for tone push-button signalling. To this end two side lobes are added to each detector, operating as DFT detectors with a main lobe for a relevant frequency of the eight nominal tone push-button signalling frequencies. This is achieved by making use in the DFT calculations of special product coefficients, which have been previously calculated for the low and high bands, respectively, of the four nominal signalling frequencies and stored in memories (9;10), for particular Kaiser-Bessel window functions and for pairs of frequencies of 603 and 1039 Hz added pairwise to the low-band and 1107 and 1805 Hz added pairwise to the high-band. These coefficients are chosen such that the maxima of these added side lobes are 1/√3-part of the maxima of the relevant main lobes. The speech detector comprises a function section 12 which adds together the correlator result other than the two strongest results as generated per cycle of 8 DFT's, and a comparator section 11 in which such a sum result is repeatedly compared with a fixed noise threshold. By means of such a speech detector the bandwidth involved in speech guarding is increased at the upper and lower sides, while the selectivity in these bands is improved.
Inventors
- 👤 Robert Jacques Marie Verbeek
- 👤 Rudolf Van Bokhorst
- 👤 Hendrikus Jacobus Dekker
- 👤 Johannes Hendrikus Maria Velthof
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 11:29
CPC Classifications
H; H04; H04Q; H04Q1/00; H04Q1/18; H04Q1/30; H04Q1/44; H04Q1/444; H04Q1/46
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
284 words
Receiving equipment which is arranged to recognize out of incoming signals a number of different frequency combinations, each composed of at least two different combinations of a number (s) of nominal voice-frequency signalling components, said equipment containing a number (s) of mutually different DFT digital signal-processing devices each having a frequency response characteristic the top of whose main lobe corresponds to one of said nominal voice-frequency signalling components situated within a frequency band as determined by one of two subgroups into which said voice-frequency signalling components are divided, and a processor which is equipped to process the results of the digital signal-processing devices, to detect two nominal voice-frequency signalling components that are received with the greatest strength, and to evaluate the other results so as to fulfil a voice-signal guard function, characterized in that the frequency response characteristic of each of the DFT digital signal-processing devices has a first side lobe and a second side lobe, each with one top, wherein the top of the first side lobe and the top of the second side lobe are situated respectively below and above the frequency band of the subgroup to which the relevant nominal signalling frequency component belongs; and the processor is equipped a) for repeatedly adding together the results of a number (s-2) of the DFT devices in such a way that a sum result is obtained that is representative of the total energy content of all detected input signals other than two nominal voice-frequency signalling components that are received with the greatest strength, and b) for comparing the sum result with a threshold value which is derived from one of said two nominal voice-frequency signalling components that are received with the greatest strength.
Claim 2
Dependent Claim
284 words
Receiving equipment which is arranged to recognize out of incoming signals a number of different frequency combinations, each composed of at least two different combinations of a number (s) of nominal voice-frequency signalling components, said equipment containing a number (s) of mutually different DFT digital signal-processing devices each having a frequency response characteristic the top of whose main lobe corresponds to one of said nominal voice-frequency signalling components situated within a frequency band as determined by one of two subgroups into which said voice-frequency signalling components are divided, and a processor which is equipped to process the results of the digital signal-processing devices, to detect two nominal voice-frequency signalling components that are received with the greatest strength, and to evaluate the other results so as to fulfil a voice-signal guard function, characterized in that the frequency response characteristic of each of the DFT digital signal-processing devices has a first side lobe and a second side lobe, each with one top, wherein the top of the first side lobe and the top of the second side lobe are situated respectively below and above the frequency band of the subgroup to which the relevant nominal signalling frequency component belongs; and the processor is equipped a) for repeatedly adding together the results of a number (s-2) of the DFT devices in such a way that a sum result is obtained that is representative of the total energy content of all detected input signals other than two nominal voice-frequency signalling components that are received with the greatest strength, and b) for comparing the sum result with a threshold value which is derived from one of said two nominal voice-frequency signalling components that are received with the greatest strength.
Claim 3
Dependent Claim
64 words
Receiving equipment as claimed in Claim 1, characterized in that each of the digital signal-processing devices is dimensioned in such a way that at the minimum frequency distance between a relevant nominal signalling frequency component and a frequency thatlimits the detection bandwidth of the nearest neighbouring nominal signalling frequency component an attenuation is introduced which in the main has one and the same magnitude.
Claim 4
Dependent Claim
43 words
Receiving equipment as claimed in Claims 1 or 2, characterized in that each of the digital signal-processing devices is dimensioned such that the tops of the relevant two side lobes are mainly 6 dB lower than the top of the corresponding main lobe.
Claim 5
Dependent Claim
43 words
Receiving equipment as claimed in any one of the foregoing Claims 1-3, characterized in that the shape of the frequency response characteristic of each of the digital processing devices is determined by a window function of the kind known as the Kaiser-Bessel function.
Claim 6
Dependent Claim
54 words
Receiving equipment as claimed in Claim 4, characterized in that the digital signal-processing devices are so dimensioned that the frequencies of the tops of the side lobes that are added to the subgroup with the lowest and highest frequency band, respectively, are located at respectively 603 and 1039 Hz and 1107 and 1805 Hz.
Claim 7
Dependent Claim
65 words
Receiving equipment as claimed in any one of the foregoing Claims 1-3, comprising a memory device for the temporary storage of a number of samples of a presented signal, characterized in that read-out means are provided for alternately reading out half the number of samples stored in the memory device, provided that upon each read-out the most neighbouring sample of a read-out sample is negated.
References Cited (Backward Citations)
FR2455405A1
Cited
GB2113880A
Cited
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