Matches 301 - 350 out of 359 < 1 2 3 4 5 6 7 8 >
Match Document Document Title
4439639 Digital circuit and method for the detection of call progress tones in telephone systems  
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...
4426555 Telephone communications device for hearing-impaired person  
A device for visually presenting communications information, communicated over the telephone network by a pair of sequential dual-tone-matrix-frequency (DTMF) signals to a hearing-impaired person's...
4412299 Phase jitter detector  
A phase jitter detector that is ideally suited for use in combination with tone receivers (e.g., tone-to-pulse converters) to provide a speech immune tone detection system or in a measuring...
4404433 Telephone call monitoring apparatus  
A telephone call monitoring apparatus is described for monitoring a subscriber's telephone to determine the time of day in which incoming or outgoing telephone calls are made and the duration of...
4403298 Adaptive techniques for automatic frequency determination and measurement  
Various implementations of a technique are presented for capitalizing on signal correlation in a manner for providing usable frequency information. In a specific embodiment, a filter (51) is...
4401860 Frequency signaling method and apparatus with dynamic compensation for frequency errors  
Frequency encoded signaling method and structure to correct for frequency error introduced in the generation of encoded signals. A sequence of frequency encoded signals are recorded on rotating...
4399536 Convolution filter arrangement for digital multifrequency receiver  
A digital multifrequency (MF) receiver for use in telephone switching systems is disclosed. Input MF signals in a PCM (pulse code modulation) format are detected by simultaneously computing the...
4395595 Digital pushbutton signalling receiver  
A digital pushbutton (PB) signalling receiver having reduced sampling frequency for reducing the operations required by digital filters. The PB receiver is responsive to an in-band audio signal...
4390843 Telephone system ring period detector  
An improved ring detector circuit is provided to discriminate between ring signals and low frequency dial signals. The circuit times the interval between pulses generated each time the incoming...
4386239 Multifrequency tone detector  
A signal recognition circuit (10) is disclosed which is capable of distinguishing between the digit tones used for dialing in multifrequency tone telephone sets, and spurious signals at the same...
4379347 Receiver for PCM-encoded multifrequency dialing signals  
To decode multifrequency dialing signals transmitted by a pushbutton-equipped subscriber station of a telecommunication system and quantized upon arrival at a central office, a receiver at the...
4366348 Method and apparatus for decoding and processing the informational content of multi-frequency signals  
An apparatus and method are described for receiving multi-frequency tone signals, such as those which are now being utilized in telephone systems, and for deriving the informational content...
4363100 Detection of tones in sampled signals  
A tone detector in the form of a digital correlator is disclosed in which PCM signal samples are delayed in a RAM for the correlation period. Using PROMs, the products of the current and delayed...
4363127 Line signaling apparatus and techniques for digital data links  
Statistical properties of a signal are used to distinguish between a voice signal and an "on hook" indication on a low bandwidth digital data link. Noise is intentionally added to the voice signal...
4354248 Programmable multifrequency tone receiver  
A multifrequency tone receiver is disclosed for detecting simultaneous tone signals in a sampled digital signal. The tone receiver includes a microprogrammed sequence controller, a time-multiplexed...
4352958 Electronically-switched multifrequency generator with transducer control  
In a multifrequency generator providing tone signaling for a telephone, the common switching functions are performed by solid state switching circuitry (1200). Improved signal transfer between the...
4333150 Signal receiving apparatus and method  
A signal receiving apparatus and method are provided to decode an input signal to determine the presence of at least one desired frequency component in that input signal. A number of signal samples...
4286326 Digital devices for spectrum analysis  
This invention relates to digital devices for spectral analysis. Signal x(t) of spectrum X(f), sampled at frequency 1/T and encoded, is processed by a temporal digital filter having a width NT...
4206323 Dual tone multifrequency signal receiver  
A system and method for detecting the presence of a tone burst and identifying the frequency signals contained within the tone burst of a dual tone multifrequency system includes an arrangement for...
4169969 Apparatus for detecting in-band signalling signals  
An apparatus comprising a stopband filter, a linear amplifier, a limiter circuit, a narrow band filter and a threshold circuit, insensitive to voice signals. When signalling signals are emitted...
4142177 Digital tone decoder system  
The digital tone decoder system includes a phase locked loop which receives an input tone signal, which may be accompanied by noise, and produces a replica of the input signal from which the noise...
4087635 Method of and system for carrying out calculations by means of a telephone set  
The invention permits to a person to make use of a computer or calculator at a distance by using a telephone to communicate with the calculator or computer. The connection may be done directly or...
4085295 Multi-frequency signal receivers  
A multi-frequency signal receiver comprising an automatic gain control circuit for adjusting the level of the multi-frequency signal, a plurality of bandpass filters for separating the output from...
4082924 Reference signal circuit in a receiver for detecting two frequencies in a multifrequency tone signal  
A reference signal circuit in a multi-frequency signal receiver for detecting the two signalling frequencies in an incoming voice frequency signal. The circuit has two paths for receiving the...
4066846 Combined rotary dial and touch-tone telephone decoding system  
A rotary dial signal processing circuit and an automatic selecting circuit for combining the rotary dial signal processing circuit with a Touch-Tone digital decoding system. The rotary dial signal...
4066848 Telephone ring detector circuit  
A telephone ring detector circuit is provided which finds particular utility in telephone answering systems. The detector circuit responds only to ring signals on the telephone line to activate the...
4064488 Sampled signal detector  
A few cycles of an input signal are correlated, or compared, with a few cycles of the input signal received at a previous interval and the interval is varied when correlation, or a positive...
4064367 Dual tone selector with answerback signalling  
A function control code sequence of signals, each comprising a pair of audio frequency tones, is transmitted from a control location to a remote station selector. Each input signal is applied to a...
4045620 Digital tone detector  
Individual tones in a tone burst of limited duration are discriminated by repeatedly counting clock pulses during a definite selected number of tone cycles to produce a count summation. The...
4042789 Tone combination detector and coincidence timer circuit  
A tone receiver for detecting a Dual Tone Multi-Frequency (DTMF) signal includes first and second digital tone detectors for the high and low bands, respectively. These detectors are of the type...
4037171 High speed tone decoder utilizing a phase-locked loop  
A narrow-band tone decoder has a controllable oscillator, connected in a fast-capture phase-locked loop, for generating a signal having a frequency determined by a control signal produced within...
4021620 Multifrequency signal receiver with digital tone receiver  
A converter, for converting a dual-tone multi-frequency (DTMF) signal produced by a TOUCH-TONE telephone to a 2-out-of-7 coded representation of the "dialed" number, includes an oscillator having a...
4021653 Digital programmable tone detector  
An improved detection arrangement for detecting the presence of a given tone in a received input signal. A reference generator, in the form of a reference clock and a programmable divider, produces...
3988687 Step-servoed tone detector  
An incoming signal (tone) and the feedback signal of a biquadratic filter are converted into square waves by zero crossing comparators. The phase state of the square waves is decoded and the...
3979562 Decoder  
An improved decoder is settable to recognize the digits of a preselected code and utilizes two complementary semi-conductor digital counters. Such counters draw very little current from their...
3936801 Multifrequency signal receiver timing circuit  
A digital timing circuit comprising integrated circuits is presented for multifrequency signal receivers in which a first counter is pulsed by a clock to generate predetermined timing intervals...
3935392 Dial pulse detection method and apparatus  
Apparatus and method for detecting the occurrence of a dial pulse signal in a telephone circuit. Transient signals within the frequency range of possible dial pulse signals are detected, and the...
3934097 Multifrequency tone detection  
A method and apparatus for detecting multifrequency tones in a received signal by summing aperiodic samples and without using bandpass filters. In a receiver capable of detecting m different tones...
3932708 Frequency-selective signal receiver for communication equipments, more particularly telephone equipments  
In a frequency-selective signal receiver for receiving at least two multi-frequency group codes and equipped with a voice-frequency trap, a broad-band frequency detector and a narrow-band frequency...
3912869 Multifrequency-to-digital converter  
A multifrequency-to-digital converter for converting a two-tone multifrequency signal into a digital signal representing the multifrequency signal is disclosed. The incoming multifrequency signal...
3875347 Multifrequency signal receiver  
A receiver for detection of multifrequency tones as used for signaling purposes in telecommunication systems. Active bandpass filters are employed with digital logic networks to make the circuitry...
3864522 AUTOMATIC TELEPHONE LOCATION SYSTEM  
An automatic telephone location system for determining the location of telephones used in making calls to telephones at emergency stations. In response to a call, the emergency station telephone...
3824345 AUDIO FREQUENCY AUTOMATIC GAIN CONTROL CIRCUIT  
An integrated circuit design for an audio frequency automatic gain control circuit, for use in telephone tone receiver circuits. To ensure stability, along with rapid response and recovery times, a...
3800096 TONE DATA RECEIVER  
A coded message receiver powered solely by energy withdrawn from telephone lines to which it is connected, monitors the lines and responds to a plurality of different signals of predetermined...
3790720 DIGITAL DECODER FOR MULTIPLE FREQUENCY TELEPHONE SIGNALLING  
A signal selected from a family of signals having different predetermined frequencies is identified, within predetermined frequency limits. In one embodiment a decoder of the digital type is used...
3763324 TONE DETECTOR SYSTEM  
There is disclosed a tone detector system which is particularly useful in communications systems for detecting audio-frequency signalling tones transmitted from one station to another. The...
3743945 LIMITER FOR MULTI FREQUENCY VOICE RECEIVER  
A multi-frequency receiver for use in telecommunications system receives tones within the audio frequency range. The tones transmitted to the receiver must be selectively separated, amplified,...
3573376 SIGNALLING SYSTEM WITH UPPER AND LOWER CASE DESIGNATIONS  
A signalling system for remote operation of a calculator which requires 22 distinguishable input signals. A standard 12-key key set is used at the local station. One key is designated a shift key,...
3470532 CODE CHECKING CIRCUIT AND MULTIFREQUENCY DATA RECEIVER  
3454720 CALL PROGRESS SIGNAL DETECTOR FOR SWITCHING SYSTEMS  
Matches 301 - 350 out of 359 < 1 2 3 4 5 6 7 8 >