Pulse or digital communications – Repeaters – Testing
Patent
1986-07-11
1988-05-03
Griffin, Robert L.
Pulse or digital communications
Repeaters
Testing
364726, 379284, 34082574, H04L 506
Patent
active
047425342
ABSTRACT:
A telephone signalling receiver comprising speech detectors for respective voice-frequency signalling components of push-button (TDK) signals which are in a frequency band divided into lower and upper frequency subgroups. Each detector calculates the Discrete Fourier Transform (DFT) of the corresponding signal frequency component, the frequency characteristic of such detector having a main lobe for such signalling frequency component and two side lobes. Such calculation employs DFT product coefficients calculated for the lower and upper frequency subgroups and which are stored in memories, such coefficients being for particular Kaiser-Bessel window functions and for pairs of frequencies in the lower and higher subgroups. The coefficients are selected so that the peaks of the side lobes are lower, such as 6 dB below, the peaks of the associated main lobes. A processor adds the outputs of all detectors other than those for the two signalling components which are received with the greatest strength, and a comparator compares the sum so derived with a fixed noise threshold. Such speech detectors provide increased bandwidth in the upper and lower frequency subgroups for guarding against spurious voice signals, while improving the selectivity in such subgroups.
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patent: 4025730 (1977-05-01), Sawai
patent: 4080661 (1978-03-01), Niwa
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patent: 4334273 (1982-06-01), Ikeda
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patent: 4479229 (1984-10-01), Wolters
patent: 4614909 (1986-09-01), Jarvfalt
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Dekker Hendrikus J.
Van Bokhorst Rudolf
Velthof Johannes H. M.
Verbeek Robert J. M.
Briody Thomas A.
Chin Stephen
Griffin Robert L.
Oisher Jack
U.S. Philips Corp.
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