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| Number | Title | Issue Date |
| 7003093 | Tone detection for integrated telecommunications processing Disclosed is an integrated tone detection processor for discriminating between tone and voice signals and determining the tones. The tone detection processor performs Automatic Gain Control (AGC) to normalize the power of the tone or voice signal. Further, the energ... | 02/21/2006 |
| 6850616 | Frequency error detection methods and systems using the same A method of detecting frequency errors exceeding a predetermined limit in a sampled signal includes the step of determining a peak amplitude of the signal at a tone frequency for a first frame of samples of the sampled signals using a filter having a first amplitude... | 02/01/2005 |
| 6839429 | Spectral optimization for communication under a peak frequency-domain power constraint System and methods for determining an optimized transmit spectra (spectral distributions of transmission power) for a set of communications channels that experience cross-talk among themselves and for transmitting data on the channels. The transmit spectra are prefe... | 01/04/2005 |
| 6771767 | Signal detector with coefficient swapping transform unit A signal detector includes a transform unit and a post processing test unit. The transform unit is adapted to a transform unit adapted to receive at least first and second frames of input samples, determine a first plurality of energy values for the first frame base... | 08/03/2004 |
| 6580792 | Signal detector with automatic gain control A signal detector includes a transform unit, a gain control unit, and an energy level threshold unit. The transform unit is adapted to receive a plurality of input samples and calculate a first plurality of delay values based on the input samples. Each de... | 06/17/2003 |
| 6493441 | Method of controlling telecommunications signalling A method for inhibiting the use of dual tones over an established voice channel of a telecommunications network. The method inhibits a call tone by removing at least one frequency selected from a group of frequencies used for in-band signaling. The method... | 12/10/2002 |
| 6484139 | Voice frequency-band encoder having separate quantizing units for voice and non-voice encoding A voice encoding device according to the present invention includes an encoder having a first quantizing block suitable for voice encoding and a second quantizing block suitable for non-voice encoding and compressively encoding input signals, a voice/non-... | 11/19/2002 |
| 6381330 | False tone detect suppression using multiple frame sweeping harmonic analysis Detection of alerting or other tone signals in a composite signal are reliably detected with an improved false tone detect suppression technique which employs the use of a moving window analysis on a subset of frequencies detected within an underlying spe... | 04/30/2002 |
| 6314175 | System and method for redirecting control of in-band signaling In a telecommunication system having a network switch capable of independently controlling inbound and outbound call legs, a system for, and method of, redirecting in-band control of signaling pertaining to a call placed by a calling party and a system fo... | 11/06/2001 |
| 6301355 | Method and apparatus for analyzing dual tone multi-frequency (DTMF) signals on a private branch exchange (PBX) switch A touch-tone receiver (TTR) simulator is disclosed to analyze DTMF signals and facilitate the investigation of call failure problems. The TTR simulator captures DTMF data received by a private branch exchange (PBX) switch and utilizes the instruction set ... | 10/09/2001 |
| 6229889 | Robust signaling tone frequency measurement Apparatus and methods for adaptively, reliably, and accurately measuring the frequency of an alerting or other signaling tone. A tone detector measures the frequency of a tone (continuous or pulsed) with a high degree of accuracy (e.g., to within 1 part i... | 05/08/2001 |
| 5867568 | Coverage of redirected calls Calls redirected off-net, which includes call forwarding and call coverage, is provided at the switch to which the call is initially directed (the principal party's switch), by monitoring the redirected off-net connection with a call classifier and listen... | 02/02/1999 |
| 5850437 | Transmission system with improved tone detection In a transmission system, a signalling tone is transmitted by a transmitter to a receiver via a transmission channel. In the receiver, a tone detector detects the presence of a signalling tone. In order to improve a reliability of the tone detector, a num... | 12/15/1998 |
| 5850438 | Transmission system with improved tone detection In a transmission system, a tone is transmitted by a transmitter to a receiver via a transmission channel. In the receiver, a tone detector is used to detect the presence of a signalling tone. In order to improve a reliability of the tone detector when th... | 12/15/1998 |
| 5809133 | DTMF detector system and method which performs frequency domain energy calculations with improved performance An improved dual tone multifrequency (DTMF) or multitone signal detector which more efficiently detects DTMF signals. For each received frame, the present invention initially performs only a portion of the Goertzel DFT algorithm for each of the possible t... | 09/15/1998 |
| 5729602 | Programmable multi-tone voice message starting system A system for detecting the presence, in an audio channel which may contain voice signals, of a tone at a frequency selectable from among a plurality of selectable frequencies. A bandpass filter receives the audio input; its center frequency is selectable ... | 03/17/1998 |
| 5694466 | DTMF detector system and method which performs improved twist computation and thresholding An improved dual tone multifrequency (DTMF) or multitone signal detector which more efficiently and reliably detects DTMF signals. The present invention performs twist computations only when the signal has become stable, thus achieving more accuracy and r... | 12/02/1997 |
| 5692040 | Method of and apparatus for exchanging compatible universal identification telephone protocols over a public switched telephone network A method of and apparatus for providing compatible universal identification telephone protocols by generating predetermined unique audio sequences recognizable by the telephone user as defining standardized Audio Icon information and distinct from and sep... | 11/25/1997 |
| 5675632 | Telephone exchange network using telephone exchanges with speech recognition A telephone exchange enables subscribers to use voice dialing more easily with existing telephone systems. The voice dialing does not require special input operations or preregistration of called parties. Rather, a subscriber can make a telephone call eas... | 10/07/1997 |
| 5638436 | Voice detection In a voice processing system, a voice detection algorithm is disclosed wherein the sensitivity is adjusted based upon whether or not tones (e.g.; DTMF) are presently being received. In an additional embodiment, the adjustment is made only when the voice p... | 06/10/1997 |
| 5619565 | Voice activity detection method and apparatus using the same A method for detecting the presence of voice, single tone and dual tone signals compares a ratio r which equals the square of the maximum value of the received signal (A max) during a sampling period divided by a measure E of the energy to three different... | 04/08/1997 |
| 5619564 | Tone detector with improved performance in the presence of speech This tone detector which is suited for dual tone multifrequency (DTMF) digit detection, separates the pairs of tones into a low frequency and high frequency group in which the other frequency group is attenuated by filtering. The amplitude of the low and ... | 04/08/1997 |
| 5588053 | DTMF detector system and method which performs static and dynamic thresholding An improved dual tone multifrequency (DTMF) or multitone signal detector which uses both static and dynamic thresholding techniques to provide an increased functional dynamic range, improved speech immunity for improved detection and reduced error, and si... | 12/24/1996 |
| 5583934 | DC level control for an electronic telephone line card DC level control for an electronic telephone line card which filters the DC component from the input audio signal, determines the gain setting of the transmit path, develops a DC adjust voltage opposite to that of the DC shift component and subtracts the ... | 12/10/1996 |
| 5535271 | Apparatus and method for dual tone multifrequency signal detection A DTMF digit detecting method and apparatus includes signal state identifier (32) for identifying whether the received signal is in a DTMF-digit-detect state, a no-detect high-energy state, or a no-detect low-energy state, digit candidate identification p... | 07/09/1996 |
| 5533118 | Voice activity detection method and apparatus using the same A method for detecting the presence of voice, single tone and dual tone signals compares a ratio r which equals the square of the maximum value of the received signal (A max) during a sampling period divided by a measure E of the energy to three different... | 07/02/1996 |
| 5519774 | Method and system for detecting at a selected station an alerting signal in the presence of speech A method and apparatus for detecting a dual tone alerting signal in the presence of speech for the purpose of initiating transfer of special service information on a telephone line is described. The apparatus includes two channels for separately detecting... | 05/21/1996 |
| 5495526 | Tone-detection method for detecting at least one tone in a dual-tone multifrequency signal, call-progress method using the same A method for detecting the presence of single tone and dual tone signals compares a ratio r which equals the square of the maximum value of the received signal (A max) during a sampling period divided by a measure E of the energy to three different thresh... | 02/27/1996 |
| 5459781 | Selectively activated dual tone multi-frequency detector A technique for improved DTMF detection utilizes a speech detector, either alone or in combination with other information from a voice processing arrangement, to adjust the sensitivity of the DTMF detector. The DTMF detector is turned completely off when ... | 10/17/1995 |
| 5426696 | Method of improving receiver sensitivity and speech immunity with DTMF-reception A method of improving the sensitivity and speech immunity of a receiver in conjunction with DTMF-reception is disclosed. The number of zero-crossings of the input signal are counted during one of a number of measuring intervals in real time at frequencies... | 06/20/1995 |
| 5416836 | Disconnect signalling detection arrangement A substantially-universal detector (FIG. 2) of far-end call disconnect-indicative tones detects the foreseeable forms of tone-based signalling of remote-end call disconnect that are likely to be employed anywhere in the world, without reconfiguration or r... | 05/16/1995 |
| 5406621 | Telephone tone analysis system In a preferred embodiment, a method of automating configuration of a voice processing system including automating telephone tone parameter determination, including the automated functions of: generating a first telephone line tone; scanning the first tele... | 04/11/1995 |
| 5392348 | DTMF detection having sample rate decimation and adaptive tone detection A method of dual-tone multifrequency (DTMF) detection which decimates and adaptively filters an input signal is provided to efficiently detect a presence of a DTMF signal. The input signal is provided to a half-band filter (14) to be decimated in frequenc... | 02/21/1995 |
| 5333191 | Detection of multifrequency tone signals A method of operating a digital signal processor to detect DTMF tones in a digital voice telephone system in which the digitally encoded signals appearing on the telephone channel are decimated to compress the spectrum to be monitored for the appearance o... | 07/26/1994 |
| 5321745 | Adaptive efficient single/dual tone decoder apparatus and method for identifying call-progression signals A process for determining the presence of either speech or one of a plurality of expected single-frequency signals on a line includes the steps of measuring the total signal energy on the line; measuring the signal energy present in each one of a pluralit... | 06/14/1994 |
| 4896346 | Password controlled switching system A password controlled switching system and method of operation for enrolling and storing passwords identifying lines and trunks of the switching system denied access thereto by other lines and trunks and which is operable upon a match of a calling party c... | 01/23/1990 |
| 4829562 | Receiver for detecting different fixed frequency signals on a telephone trunkline A signalling receiver has its signal input (E) connected to a central-office trunk (a, b) in a trunk junctor and includes a variable bandpass filter (BP) connected to a clock line (TL). The signal input (E) is connected via an attenuator (DG) to a variabl... | 05/09/1989 |
| 4763350 | Facility for detecting and converting dial information and control information for service features of a telephone switching system In a telephone switching system, a multifrequency code receiver unit is replaced by a voice-controlled dial signal receiver unit connected to the switching network via an adapter unit. The voice-controlled dial signal receiver unit contains a voice recogn... | 08/09/1988 |
| 4621358 | Remote switch for telephony switching system A telephone switching network including a remote line switch that couples digital voice signals from a plurality of subscriber lines onto a lesser number of communications links connected to a central office. The remote line switch also includes an intra-... | 11/04/1986 |
| 4161630 | Circuit arrangement for use in telephone systems An automatic telephone exchange including registers for the setting up of calls over outgoing junctions by multi-frequency code--(M.F.C.) signalling, in which the junctors are accessible via M.F. control equipments which are connected to the registers via... | 07/17/1979 |
