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7136434 Apparatus and method for detecting energy of tone signal  
An apparatus and a method for detecting the energy of a tone signal. A pre-process unit takes absolute values of transmitted samples and outputs the values to a delay unit for delaying the...
7111030 Method of detecting pilot tones in a noisy signal  
This invention relates to detecting a pilot tone in an optical fiber. In the method described in the invention, computational complexity is reduced significantly by almost completely removing the...
7023981 Method and apparatus for signal detection  
A signal detector for detecting a signal having a first nominal frequency, F 1 and a second nominal frequency F 2 , the signal intermixed with an interfering signal to form a composite signal, the...
6954771 Adaptive line enhancer  
An improved adaptive line enhancer includes an adaptive Gray-Markel lattice notch filter having an adaptive notch frequency, in which the notch frequency is determined according to a notch...
6898214 Technique for monitoring SONET signal  
A technique for performance-monitoring of a standard SONET signal involves first converting the optical signal to an electrical signal, removing in the framing signal time slot the framing signal...
6873701 System and method for DTMF detection using likelihood ratios  
A system and method for determining DTMF coefficients stores a plurality of reference templates, at least some of said reference templates representative of likelihood ratios. A plurality of LPC...
6782095 Method and apparatus for performing spectral processing in tone detection  
A general purpose network tone detection method and apparatus that allows the precise and accurate recognition of North American tones (MF, DTMF (Dual-Tone Multifrequency), and CPT (Call Progress...
6574334 Efficient dynamic energy thresholding in multiple-tone multiple frequency detectors  
An apparatus for determining energy threshold detection values for detecting at least one tone having a known frequency and duration in an input signal. The input signal is input over a period of...
6424925 Circuit and method for detecting a tone signal  
A tone detector includes at least one circuit (hereinafter “single phase reference matcher”) that not only performs a convolution of an input signal with a reference signal, but also compares...
6353629 Poly-path time domain equalization  
Improved techniques for time domain equalization are disclosed. The improved techniques include (i) improved time domain equalization techniques referred to as poly-path time domain equalization...
6332151 Time discrete filter  
A decimating time discrete filter comprises transform means (2) for transfornming a real valued input signal i into a complex signal u represented by its real part Re{U} and its imaginary part...
6304133 Moving average filter  
A moving averaging filter which does not propagate a calculation error is provided reducing the size of the hardware. This moving average filter has a data holding unit for holding multiple...
6236838 System for superresolution based estimation of control signals in a communications system  
A system for wireless communication between a base station 30 and one or more remote stations 32 and 34 wherein a desired signal has associated therewith an identifier tone (a SAT in the vernacular...
6195675 Tone detection using discrete fourier transform techniques  
Supervisory audio tone (SAT) in a receive signal in a wireless communications system is detected using a discrete Fourier transform (DFT) supplied with samples of a filtered and decimated signal...
6122652 Tone and periodical signal detection  
Algorithms for quickly and efficiently detecting a periodic signal such as a DTMF signal in a telephone system are described. The algorithms, implemented in a tone detector, detect the periodicity...
6026419 Single tone signal detector  
A signal detector for detecting a narrow-band signal of a desired frequency, using an adaptive type FIR filter having two filter coefficients, is disclosed. Using this filter, the input signal of a...
6023191 Method and apparatus for detecting an input signal  
A level detector detects an input signal level. A rectifier (210) receives the input signal and provides a rectified signal. A prefilter (220) receives the rectified signal and attenuates high...
6003055 Digital filter interpolation circuit  
An interpolation circuit for a digital filter which is small in circuit scale, operates at a high speed and is low in power consumption. The digital interpolation filter circuit includes front-end...
5999954 Low-power digital filtering utilizing adaptive approximate filtering  
A method of digital filtering and a digital filter having a filter response with a predetermined filter order. The filter response produces a predetermined set of filtered output samples defining...
5916301 Sample rate conversion for synchronous variable rate  
The concept of integer ratio sample rate conversion is extended to fractional values, where the exact ratio is expressed as M+N/D!/L with L being a constant. This methodology allows sample rate...
5910906 Digital single-frequency tone detection in presence of aliases  
The invention is a method for performing tone detection on a digital signal processor (DSP) that may be used in the presence of tone aliases caused by inadequate anti-aliasing filtering. The method...
5765125 Detection of tones while minimizing incorrect identification of other sounds as tones  
A first validation circuit utilizes residual energy unaccounted for by a linear predictive coding model for a specified order of model as a criteria on which to make a validity determination of...
5353344 Method of determining levels at given frequencies of a VF signal  
A dialing receiver (1) for determining multifrequency dialing signals on an incoming signal in a telecommunication switching system, including a sampling circuit (4) for taking N values of the...
5353346 Multi-frequency signal detector and classifier  
A method and apparatus for detecting and classifying signals that are the additive combination of a few constant-amplitude sinusoidal components, herein called N-tones. The attributes of this...
5274579 Digital tone detector  
A digital tone detector utilizes pseudo sinusoidal quadrature reference signals in combination with a unique summation rule for summing the resultant quadrature accumulations to obtain a...
5251256 Independent hysteresis apparatus for tone detection  
To detect tones for call progress monitoring, hysteresis apparatus is provided whereby the output of a typical tone detector such as a comparator operating in conjunction with a selective filter is...
5198992 Method and apparatus for improving wideband detection of a tone  
An in-phase signal is sampled at an input of a first analog-to-digital converter (41), and a quadrature signal is sampled at an input of a second analog-to-digital converter (42). The output of the...
5189634 Digital signal processing apparatus for detecting a frequency component of digital signals  
A digital signal processing apparatus is disclosed. The apparatus is particularly suited for detecting a digital signal containing a frequency component in a noisy environment. It uses a...
5138569 Dual tone multi-frequency detector  
An apparatus for identifying a first tone and a second tone present in a dual-tone signal, the first tone being selected from a group of tones located within a low band and the second tone being...
5136531 Method and apparatus for detecting a wideband tone  
A method of detecting a wideband tone, having a nominal frequency but occurring anywhere within a wide range of frequencies, includes a step of bandpass filtering input data. The bandpass-filtered...
5119322 Digital DTMF tone detector  
A digital dual tone multi-frequency (DTMF) tone receiver having a detector circuit for scanning incoming audio signals for possible presence of DTMF tones, and a verifier circuit for verifying the...
5087866 Temperature compensating circuit for LVDT and control system  
A linear variable displacement transducer (LVDT) has a core connected to an actuator such as a torque motor. The outputs of the LVDT are demodulated and subtracted to provide a displacement signal...
4989169 Digital tone detector using a ratio of two demodulators of differing frequency  
A digital tone detector receives a modulated input signal selectively containing at least one tone signal component. Two demodulator circuits each demodulate the input signal wherein one...
4947361 Narrowband parameter estimator  
A narrowband parameter estimator circuit is described which can be used to estimate the frequency and the relative power of narrowband interference tones which reside in a wideband information...
4849989 Data modem receiver  
In a data modem receiver (80) the received signal is digitized in an A/D-converter (84), the output of which is applied to notch filter means (88, 96) which eliminates secondary channel signals,...
4769610 Tone decoder  
This tone decoder utilizes three correlators for detecting the presence of a desired tone signal. A main correlator correlates to the desired tone frequency, while two side correlators are used to...
4709344 Programmable multifrequency digital tone receiver  
A circuit arrangement for filtering input signals carried on PCM channels. The circuit arrangement includes a plurality of digital signal processors arranged in a parallel manner each having a set...
4698769 Supervisory audio tone detection in a radio channel  
Supervisory audio tones received from a mobile telephone unit are converted from analog to digital form. The tone is then converted to a complex number by bifurcating the tone path and multiplying...
4674103 Method and arrangement for detecting the presence of a training signal in a modem receiver  
For rapidly detecting a periodic training signal in a modem receiver, delay line storage (21) is provided for a signal section which is equal to one training signal period (qM samples) plus an...
4630299 Digital circuit for decoding digitized, demodulated FM stereo signals  
A simple digital filter having only a single multiplier operates to extract the pilot tone from a demodulated and digitized FM stereo signal. The number of poles in the filter is chosen so that the...
4590583 Coin telephone measurement circuitry  
A mechanized system distributing the access, test and communication functions to the point of testing, typically the centralized switching facility serving the telephone loops and equipment to be...
4563681 Tone receiver for digital data communication systems  
A device for detecting the presence of an alarm tone of a given frequency within a received signal carrying digital data in addition to said tone. The receiver comprises an analog-to-digital...
4539692 Digital automatic gain control circuit for PCM signals  
A digital tone detector circuit characterizes the received PCM encoded signals as one of a plurality of call progress tones, voice signals or silence. The PCM signal is linearized and normalized to...
4539646 Tone detection arrangement  
A multi-tone sequential call signal detector in which a microcomputer is used to detect the tones of a received signal by simulating digitally the response of analogue tuned circuits. The detector...
4534041 Digital circuit for determining the envelope frequency of PCM encoded call progress tones in a telephone system  
A digital tone detector circuit characterizes the received PCM encoded signals as one of a plurality of call progress tones, voice signals or silence. The PCM signal is linearized and normalized to...
4534043 Test tone detector apparatus and method modem using same  
The presence of a predetermined pure sinusoidal signal is detected by periodically sampling the actual value of an input electrical signal and, based thereon, predicting what the expected value of...
4513385 Apparatus and method for suppressing side lobe response in a digitally sampled system  
A decoder circuit is provided which employs digital sampling and correlation apparatus to detect the presence of a received tone signal exhibiting a predetermined frequency. Samples of received...
4442500 Narrow band digital filter  
A narrow band digital filter is disclosed for rejecting all undesired frequencies, providing a binary signal indicative of when the input frequency is within an acceptance band. The digital filter...
4408284 Signal processing system  
A signal processing system and technique is disclosed for detecting the pence of a desired frequency signal particularly that of a sine wave, in a noisy environment. The signal mixed with noise is...
4351032 Frequency sensing circuit  
A digital circuit for sensing a frequency component F 0 in an applied signal. The amplitude of an input signal is sampled at a clock rate that is N times F 0 and each amplitude sample is encoded...
Matches 1 - 50 out of 60 1 2 >