Abstract: A line circuit utilizing a differential amplifier whose output is regulated to zero volts D.C. (when the subscriber's set is off-hook) by a negative feedback circuit, for controlling a voltage controlled power supply which provides a constant current feed to the subscriber's loop. The differential amplifier also transmits audio signals received from the subscriber's loop directly to a PABX via an unbalanced terminal. When the loop range exceeds a predetermined threshold, the circuit reverts to a voltage feed operation thereby allowing operation over long loop lengths and the ability to provide on-hook CLASS services.
Abstract: A dummy listener and right and left speakers 13 and 14 are disposed in an anechoic room as a model of the layout of those a car cabin 15 or the like. Transfer functions ALL, ALR, ARL and ARR in a space ranging from the speakers 13 and 14 to the right and left ears of a listener 16 in a car cabin 15 or the like are calculated from impulse response series aLL(t) to aRR(t) obtained when pulse sounds are respectively emitted from the speakers 13 and 14. A correction circuit 10b contains correction transfer functions H11, H12, H21 and H22, which are obtained by an inverse matrix of a 2-row and 2-column regular matrix of which the elements are the transfer functions ALL, ALR, ARL and ARR. Audio signals SL and SR on which head related transfer functions are superimposed are applied to the correction circuit 10b, and the output signals of the correction circuit 10b are supplied to the speakers 13 and 14.
Abstract: An application programming interface (API) enables a telephone to utilize the hardware resources of a computer that is connected to the telephone in a master/slave relationship that causes the computer to function in the manner of a peripheral to the telephone. Specifically, the telephone attached to the computer can utilize the relatively large memory capacity of the attached computer to store excess telephone-specific data and can utilize the relatively high sophistication of the processing capability of the connected computer to perform intensive data processing operations. The API allows the functionality of the telephone to be extended without requiring a telephony-equipped computer.
Abstract: Method and device for echo compensation with a common-frequency transmission method in duplex mode over a two-wire line, an echo compensation filter which has adjustable coefficients and is embodied as an FIR filter being arranged between the transmitter output and receiver input and an IIR filter with adjustable coefficients, whose coefficients can be determined as a function of the coefficients of the FIR filter, being additionally provided.
Abstract: In one embodiment, a system is provided for processing an input signal communicated on a telephone line, the input signal including a first component associated with a first frequency band, a second component associated with a second frequency band higher than the first frequency band, and a third component associated with a third frequency band higher than the second frequency band. The system includes a first filter to receive the input signal and to pass a first signal substantially comprising the second component, a second filter to receive the input signal and to pass a second signal substantially comprising the first and third components, and a third filter to receive the second signal and to pass a third signal substantially comprising the first component according to an input capacitance of a fourth filter that limits the ability of the third filter to pass the second component.
Abstract: A telephone receiver circuit with sidetone signal generation controlled by voice activity detection in accordance with the present invention uses the voice activity detector (VAD) to detect the presence of voice activity within the microphone signal and dynamically adjust the sidetone signal generation to compensate for noisy environments by eliminating or reducing the sidetone signal in the absence of voice activity. Hence, a sidetone signal is generated in the presence of voice activity, when feedback is required, while the sidetone signal is not generated in the absence of voice activity, since audio feedback for the user is not required then.
Abstract: An active noise control system is provided to specify an input transducer, an error transducer, an output transducer and an active noise controller for generating an anti-phase canceling acoustic signal to attenuate an input noise and to output a reduced noise. The active noise control system also performs on-line secondary path modeling. For this purpose the active noise control system comprises, in addition to known systems, a secondary path change detection circuitry (6), a signal distinguishing circuitry (7) and an auxiliary noise control circuitry (8), all of them being used to model said secondary path.
Abstract: Apparatuses and methods are disclosed for communications using current detection. According to one embodiment, a transmitter generates a signal on a transmission line by switching between two power sources. According to one embodiment, the transmitted signal is a balanced signal. Under an embodiment, a signal that has been transmitted on the transmission line is received by a receiver that includes a current detector, and the receiver detects the signal by sensing changes in current on the transmission line. According to one embodiment, the current detector includes a sensor that senses changes in the magnetic field generated by changes in current in the transmission line.
April 27, 2001
Date of Patent:
January 11, 2005
Stephen Roy Rumbaugh, Garth Wayne Haslam
Abstract: A method and apparatus that performs specific automatic gain control in an echo canceller (16). The disclosed method and apparatus utilize a low complexity algorithm that performs automatic gain control to achieve greater speed of convergence of the echo canceller (16) and an increased ability to distinguish between near-end speech and echo through the use of specific automatic gain control. A double talk threshold of the echo canceller is adjusted by using, in part, computed gains of inbound and outbound signals internally within the echo canceller in order to adjust the echo canceller double talk threshold.
Abstract: A terminating device for interconnecting service provider wiring with subscriber wiring includes a base, a customer bridge, a removable cover and insulation displacement contacts for terminating the service provider wiring and the subscriber wiring. The insulation displacement contacts for the subscriber wiring are housed within the customer bridge and terminate the subscriber wiring by moving an actuating arm from a disconnected position to a connected position. The insulation displacement contacts for the service provider wiring terminate the service provider wiring by moving a stuffer from a disconnected position to a connected position. The cover includes a locking slide having a movable clasp for deterring unauthorized access to the customer bridge, while permitting authorized access. A plug on the cover and a jack on the base each have a resilient seal that telescope together to effectively seal test contacts located within the jack when the plug is inserted into the jack.
Abstract: A method and apparatus is capable of detecting the presence of a non-linear echo path as well as transitions from non-linear echo path to linear echo path and vice versa. Additionally, when non-linear echo path is detected, the echo canceller (12) is configured to follow a prescribed logic routine that combats possible echo leak-through as a result of compromised cancellation due to non-linearity. This prescribed logic routine affords the echo canceller (12) protection against non-linear echo path by preserving an already converged state of the echo canceller (12) from possible divergence due to the occurrence of non-linearity in the echo path and thereby prevents echo leak-through that would occur due to divergence of the echo canceller (12).
Abstract: Each of multifunctional telephones has a common hold button for accepting a hold/hold release instruction of a communication partner (extension) under transfer communication; a central processing equipment controls each part of a private branch exchange so that the transfer communication partner concerned is held in accordance with a hold instruction from a multifunctional telephone under transfer communication; the information of a hold target (extension) is registered into a hold information registration area; in accordance with a hold release instruction from a multifunctional telephone holding a communication partner, the information of the communication partner specified by the instruction is searched from the hold information registration area; and the holding of the communication partner specified by the searched information is released to connect the communication partner to the multifunctional telephone concerned, whereby the communication partner (extension) under transfer communication can be held
Abstract: A method and apparatus enables echo reduction in a full duplex transceiver system. A replica current is subtracted from a receiver via a first differential circuit path that adaptively matches a time constant associated with a second differential circuit path that connects the receiver with an external data line.
Abstract: A low-pass filter of over-sampling type oversamples an input digital audio signal T1 and filters and removes the low frequency components of the produced aliasing noise. A spectrum analyzer circuit calculates the spectrum intensity of a predetermined band of an output signal from the low-pass filter. An expanded signal generating circuit generates an expanded signal having frequency components of the output signal from the low-pass filter. A level control circuit controls the level of the expanded signal according to the spectrum analyzer circuit. An adder adds the level-controlled expanded signal to the output signal from the low-pass filter thereby to generate a digital audio signal T2.
January 12, 2001
Date of Patent:
December 7, 2004
Matsushita Electric Industrial Co., Ltd.
Abstract: A filtering device (50) for active filtering at a customer premises includes an input interface that receives telephone signals and digital data signals communicated from a central office (14) using a telephone line (12). The filtering device (50) further includes an active low-pass filter (60) that receives the telephone signals, the digital data signals, and electrical power from a power source. The active low-pass filter (60) attenuates the digital data signals and passes the telephone signals using the electrical power. The filtering device (50) also includes an output interface that receives the telephone signals from the active low-pass filter (60) and communicates the telephone signals to a telephone (42).
Abstract: A base band echo cancellation method and apparatus utilizing Laguerre echo estimation. The method begins with a series of transmitted symbols that are stored in a buffer. The buffer is segmented into a head portion and a tail portion. The symbols in the tail portion are passed through a Laguerre or IIR filter and then reinserted into the tail portion of the buffer. An echo estimation signal is generated based on the symbols in the buffer. The apparatus includes a transmit symbol buffer that is coupled through a modulator to a Laguerre or IIR filter. A demodulator couples the filter back to the buffer. An echo estimator is also coupled to the buffer.
Abstract: Tone generator LSI generates a subframe start signal to be interruptively given to a microprogram, by which the microprogram is activated to issue an interrupt signal to a device driver. In response to the interrupt signal, the device driver prepares control data for use in a next frame. The microprogram receives control data from a RAM at the beginning of each frame and calculates control data for individual samples of the frame on the basis of the received control data as well as control data generated for the last sample of an immediately preceding frame, so as to create a plurality of samples of tone data for each subframe. The thus-created tone data are temporarily written into a buffer and then read out from the buffer in accordance with predetermined clock pulses.
Abstract: A digital subscriber line and POTS voice interface between a telephone line and central office equipment is provided. For POTS band frequencies, a reactive impedance coupled across the two wire interface of the POTS line card, and serially coupled to the line side of the DSL coupling transformer, has an open state magnitude. The magnitude of the line side windings of the DSL coupling transformer is low at POTS band frequencies. POTS band signal power is therefore delivered to the POTS line card. For DSL band frequencies, the reactive impedance across the POTS line card has a closed state magnitude. The POTS line card is therefore essentially short-circuited at DSL band frequencies, and DSL band signal power is delivered to the DSL modem. The frequency band in which the reactive impedance transitions from an open state magnitude to a closed state magnitude corresponds to the frequency band between the POTS frequency band and the DSL frequency band.
Abstract: A digital direct access arrangement (DAA) circuitry may be used to terminate the telephone connections at the user's end to provide a communication path for signals to and from the phone lines. Briefly described, a means for providing a proper hookswitch transition for a variety of international phone standards is provided. The invention may also be utilized with means for transmitting and receiving a signal across a capacitive isolation barrier. More particularly, a DAA circuitry may be utilized which satisfies many or all hookswitch transition standards without the use of additional discrete devices. The hookswitch transition standards may be satisfied by ramping down the current flowing through the hookswitch prior to transitioning the hookswitch state. In this manner the hookswitch current change as a function of time (di/dt) may be decreased. Thus, the current through the hookswitch may be actively controlled prior to switching the hookswitch from an off-hook condition to an on-hook condition.
July 2, 1999
Date of Patent:
November 23, 2004
Silicon Laboratories Inc.
George Tyson Tuttle, Jeffrey W. Scott, Navdeep S. Sooch, David R. Welland
Abstract: A musical garment has a plurality of interior pockets disposed on two interior portions of the garment for generating extemporaneous music by hand-impact with a selective pocket portion. Each interior pocket is secured via hook and loop fasteners and includes a sound generating piezoelectric transducer electrically connected thereto for producing multiple signals to a sound generating module. The piezoelectric transducers are sensitized or calibrated to produce a sound having a different sound characteristic compared with other piezoelectric transducers. The sound generating module is removably housed within an interior auxiliary pocket of the garment and utilizes a multiplexer to provide serial output or music for subsequent recording or listening. An acoustic screen is disposed on an exterior surface portion of the garment pocket for acoustically transmitting sound generated from the module.