Facsimile and static presentation processing – Static presentation processing – Attribute control
Patent
1983-06-20
1985-04-16
George, Keith E.
Facsimile and static presentation processing
Static presentation processing
Attribute control
455 2, 328110, 324 77G, 381 56, H03K 526, H04N 702
Patent
active
045119171
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method and apparatus for determining the agreement between an analysis signal and at least one reference signal.
BACKGROUND ART
The object of the present invention is to propose a method and provide an apparatus for monitoring, where a characteristic signal from the apparatus, process or the like which is to be monitored is utilized for analysis.
The invention is particularly suitable for use in monitoring apparatus and processes having specific sound spectra, so that audio signals can be utilized for analysis.
It is thus possible to determine with the aid of the invention whether a given signal agrees with one or more given signals, and in the latter case which one of the signals it agrees with.
DISCLOSURE OF THE INVENTION
The analysis takes place such that the signals are smoothed and pulse trains corresponding to said smoothed signals or envelopes are generated, a predetermined number of consecutive agreements in the pulse train being required for the signals to be considered in agreement. This is a safety measure so that the signals will not be registered as being in agreement with randomly coinciding pulses in the corresponding pulse trains.
The method in accordance with the invention can be utilized for comparing a signal with an optional number of given signals, the apparatus in accordance with the invention being built up with a corresponding number of parallel branches for analysis of the signals and comparison of the analysis signal with each of the given signals.
A preferred embodiment of the apparatus in accordance with the invention, selected here as an example, will be described in the following in conjunction with the appended drawings in which
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of the principal construction of the apparatus in accordance with the invention in an embodiment for two reference signals, and
FIG. 2 is an example of the use of the apparatus in accordance with the invention for automatic debiting of utilized video service.
BEST MODE FOR CARRYING OUT THE INVENTION
To build the smoothed signal or the envelope of the signal which is to be examined it is fed to a rectifier 2 and the rectified output signal is filtered in a bandpass filter 4, the passband of which is between 0.5 and 10 Hz, see FIG. 1. It has been found advantageous for the subsequent signal analysis to work within this low-frequency range, inter alia from the noise elimination aspect. The signal DC voltage level is also cut away in the filter 4.
The rectifier 2 comprises two operational amplifiers, diodes and resistances, and the filter 4 is an active filter with an operational amplifier.
The signal envelope or smoothed signal obtained from the filter output is applied to one input of a comparator 6. A threshold signal U.sub.Ref 1 is applied to the other input of the comparator 6 to prevent undesired changes of the state of the comparator due to noise. An output pulse is obtained from the comparator when the input signal exceeds the applied threshold signal and the pulse length is determined by the duration of this state.
The comparator 6 is an operational amplifier. For each of the reference signals A and B in FIG. 1 there is a like circuit 8 and 10, respectively, comprising rectifier, bandpass filter and comparator.
The threshold signal U.sub.Ref2 to the comparators in the reference signal circuits 8, 10 is somewhat higher than the threshold signal U.sub.Ref1. The output pulses from the comparators in the reference signal circuits 8 and 10 will thus be somewhat narrower than the output pulses from the comparator 6, and the reference signal pulses will be contained within the pulses from the comparator 6.
The output pulse train from the comparator 6 is applied to the data input of two D flip-flops 12, 14. The output pulse train from the reference signal circuits 8 and 10 are applied as clock signals to the flip-flops 12 and 14, respectively. The flip-flops 12, 14 go to a one state (send an output pulse) for concordant signals. The
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Kohler Hans O.
Stromvall Sten K.
George Keith E.
Kohler Hans Olof
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