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Abstract

A method and apparatus for determining concordance between an analysis signal with at least one reference signal. The smoothed signals or envelopes are formed of a signal which is to be examined and at least one reference signal. A pulse train is generated for each of the smoothed signals or envelopes, and comprises pulses present during the time for a predetermined polarity of the smoothed signal or envelopes relative a threshold signal. The pulse trains are compared at regular intervals with each other, simultaneous coincidence of pulses in both trains at a predetermined number of consecutive comparisons constituting the criterion that the signals which are to be examined are in concordance with the reference signal. For carrying out this signal examination there are circuits means (2, 4) adapted for forming the smoothed signals or envelopes of the signals. The outputs from said means are connected to one input of a comparator (6) for each signal. A threshold signal (U.sub.Ref1, U.sub.Ref2) is applied to the second input of the comparators for generating an output pulse train comprising pulses generated at a predetermined polarity of said smoothed signals or envelopes relative the threshold signals. Circuits (12, 14, 16, 18) are further adapted for comparing the pulse trains and registering simultaneous coincidence of pulses in the two trains for a predetermined number of consecutive comparisons as the criterion that the examined signal and a given reference signal are in concordance. The invention is primarily intended for utilizing in automatic debiting of utilized video service in a hotel or the like. The invention may also be used for monitoring processes or machines which have specific sound spectra for faults.

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First Claim