Abstract: A headset has an earcup with front opening adjacent to an annular cushion formed with a plurality of openings facing the inside of the earcup that acoustically couples the earcup volume to the cushion volume. A driver is seated inside the earcup with a microphone adjacent to the driver. Active noise reducing circuitry intercouples the driver and microphone. An acoustic load that may comprise a wire mesh resistive cover and/or air mass adjacent the microphone is constructed and arranged to reduce the effect of resonances in the earcup volume.

Abstract: This invention provides a method for replacing terminators in a backplane of a telecommunication switch such that the telecommunication traffic carried on a line does not require a separate routing of the traffic by the switch operator to another line card. Using this methodology, a switch operator may save a significant amount of time when a terminator needs to be replaced due to routine maintenance or becomes faulty and has outlived its useful life. The telecommunication traffic carried by the line card is typically switched to protected mode status prior to replacing the terminator on the front side of the backplane. A terminator having a mirror image of electronic circuitry of the terminator being replaced is attached to pins located on the rear side of the backplane. The line card is removed and the terminator on the front side of the backplane is replaced. The line card is inserted back into the slot in the backplane, and the terminator on the rear side of the backplane is removed.

Abstract: An audio apparatus for reducing white noise automatically detects when a microphone is connected, and when the microphone is not connected, to a microphone input jack. If the microphone is not connected to the microphone input jack, microphone input of the audio apparatus is automatically muted to reduce white noise.

Abstract: A headset/headphone sensing jack (203, 208, 210). A two-channel sensing circuit (210) is provided which detects whether a headphone (101) or headset (103) is installed. By employing an impedance sensing circuit (210), it is possible to use a single common 2.5 mm jack (120) for both radio and telephony operation. Formerly, two separate jacks would be required for both functions. An electronic device (50) according to the present invention is further capable of switching between AM/FM radio and telephone modes depending on whether a particular headpiece (101, 103) is installed.

Abstract: An adaptive noise rejection method and apparatus. An information signal having an information component and a repetitive noise component having a varying characteristic frequency is delayed the information signal by a reference delay time that is equal that is equal to a predetermined number of periods of the characteristic frequency to form a delayed information signal. The delayed information signal is subtracted from the information signal to form a processed information signal in which the information component is substantial and the noise component is negligible. The amplitude of the noise component of the processed information signal is constantly monitored. The delay of the information signal is varied as the characteristic frequency of the noise component changes so as to maintain the amplitude of the noise component of the processed information signal at a predetermined level.

Abstract: A Wireless Concealed Transmitter Stereo Center Speaker System includes a concealed transmitter unit installed a center speaker, and two receiver units installed in two rear speakers, wherein the concealed transmitter unit includes an automatic audio level regulating circuit to regulate the audio level of the output signal of audio equipment to a predetermined range, a power control circuit controlled by the output signal of the audio equipment to provide the necessary working voltage, and an inductance antenna to transmit stable output signal from the audio equipment to the receiver units of rear speakers; the receiver units are of low working voltage design, including an automatic 24-time frequency divider circuit to effectively discriminate left and right sound tracks, and an auto-shut off circuit to automatically cut off power supply from either an alternating current source or battery power supply when the audio equipment does not work; the concealed transmitter unit and the receiver units further use a r

Abstract: A two-step training method for the estimation filter in the echo cancellation (EC) path of the analog front-end (AFE) circuit for a modem, such as an asymmetric digital subscriber line (ADSL) modem. During the first step, the coefficients of a filter that is preferably equivalent to the combination of the EC path and the receive (RX) path in the AFE circuit are determined with the EC estimation filter held fixed and the transmit (TX) path in the AFE circuit disabled. During the second step, the TX path is enabled and the coefficients of the EC estimation filter are determined using the path equivalent filter generated during the first step. The two-step training method takes into account variations in the operating characteristics of components in the various processing paths in the AFE circuit to converge on satisfactory coefficients for the EC estimation filter within an acceptable number of training symbols.

Abstract: A digital signal processing algorithm to cancel howling in a telephone circuit, the telephone circuit being characterized by a receive path and a transmit path in an effective closed loop configuration. The algorithm monitors input samples taken from the receive path and, if a howling signal is detected, controlled amounts of attenuation are introduced to the loop until howling is cancelled. In a preferred embodiment a prediction logic is included in the algorithm to verify the howling signal.

Abstract: A line card for coupling to customer premises equipment at a termination for detecting hook condition in a telephone system, the line card comprising an interface for transmitting and receiving an analog signal with the telephone line, an AC ring signal generator for generating a ring signal at the customer equipment, a DC signal generator for generating a DC signal when said customer equipment is off hook, and a circuit for determining the duty cycle of a loop current in the customer equipment (telephone) for determining the hook status of the customer equipmen.

Abstract: A noise-reducing resonant chamber sound pick-up for electronic stethoscopes is claimed. It consists of a resonating chamber (24) which acoustically preamplifies the selected frequencies of heart sounds, 50-150 hz, and bruits of breath or blood, 150-500 hz, while rejecting ambient sounds. A skin contact (34) has elastic foam support (14), whose rigidity is varied by varying the applied pressure, in order to select the preamplified band of sounds. The other side of the resonating chamber contains a sound transducer (10) largely encased in heavy malleable metal (12) that absorbs sound not coming from the chamber. A damping vent hole (26) shapes the band of preamplified sounds. The resulting superior signal-to-noise ratio permits two, small chambers to be used in a stereophonic chest piece little larger than that of a conventional stethoscope, with better amplification enabling examination through clothing or surgical dressing even in heavy persons.

Abstract: A signal detector includes a transform unit and a cross-frame energy level unit. The transform unit is adapted to receive at least a first and a second frame of time domain input samples. The transform unit generates at least a first frequency energy value for the first frame and a second frequency energy value for the second frame based on the time domain input samples. The cross-frame energy level unit is adapted to compare the first frequency energy value to the second frequency energy value to determine the presence of a first tone in the time domain input samples. A method for detecting a signal includes receiving at least a first and a second frame of time domain input samples. At least a first frequency energy value for the first frame and a second frequency energy value for the second frame are generated based on the time domain input samples. The first frequency energy value is compared to the second frequency energy value to determine the presence of a first tone in the time domain input samples.

Abstract: A communication system is provided with a power supply budget such that portions of a phone line side circuit are powered from the TIP and RING phone lines while using standard electronic devices for the hookswitch circuits and the diode bridge circuit. For example, low voltage converters in the phone line side circuit are powered from the phone line. The low voltage converters operate off a low voltage power supply of approximately 2.5 V or less, more preferably operate off a low voltage power supply of approximately 2.0 V or less, and in one embodiment 1.9 V converters are utilized. In one embodiment, the communication system further includes a capacitive isolation barrier system for isolating the phone line side circuitry.

Abstract: A system for improving a spatial effect of stereo sound or encoded sound when producing three dimensional image sound signals from signals of stereo channel includes a spatial effect enhancing portion where a signal for enhancing spatial effect and directivity of sound is produced, a band enhancing portion where a signal for enhancing a signal component of the stereo channel signal in a low frequency range and for maintaining the signal component in a middle frequency range is generated, and a matrix portion where the output signal of the spatial effect enhancing portion, the output signal of the band enhancing portion and the stereo channel signal are calculated in a matrix manner, so that the spatial effect of sound is improved using a differential component between left and right side channel signals.

Abstract: A second-order adaptive differential microphone array (ADMA) has two first-order elements (e.g., 802 and 804 of FIG. 8), each configured to convert a received audio signal into an electrical signal. The ADMA also has (i) two delay nodes (e.g., 806 and 808) configured to delay the electrical signals from the first-order elements and (ii) two subtraction nodes (e.g., 810 and 812) configured to generate forward-facing and backward-facing cardioid signals based on differences between the electrical signals and the delayed electrical signals. The ADMA also has (i) an amplifier (e.g., 814) configured to amplify the backward-facing cardioid signal by a gain parameter; (ii) a third subtraction node (e.g., 816) configured to generate a difference signal based on a difference between the forward-facing cardioid signal and the amplified backward-facing cardioid signal; and (iii) a lowpass filter (e.g.

Abstract: A telephone set, where the state of an own-telephone-set is on-hook, the off-hook state of a parallel-telephone-set is detected by comparing telephone-line voltage value with a first standard voltage value. In the state where the own-telephone-set is off-hook, the off-hook state of the parallel-telephone-set is detected by the following method, i.e., the telephone-line voltage value is measured in detail and a second standard voltage value for judging the off-hook state of the parallel-telephone-set is determined and the voltage value is stored in place of the first standard voltage value while the own-telephone-set is off-hooked, then if the line voltage value exceeds the second standard voltage value, the parallel-telephone-set is regarded as off-hook.

Abstract: A communication terminal comprising a receiving path and a sending path linked to the communication line, the receiving path being connected to a system able to detect, during a communication, an alert signal (e.g., a CAS signal) sent by a station (e.g., the local telephone exchange station or central office) upon any new call or connection request for the terminal and able to allow reception by the terminal, e.g., of data related to each new caller, by interrupting temporarily the presently existing communication, the terminal including a detector (7) able to detect any activity or any signal transmission, and/or the absence of the same, in the sending path (3) of the terminal (1) and to deliver a corresponding information signal (IS) to the signal detection system (5), the latter adjusting its detection method or mode or selecting a corresponding detection subsystem accordingly.

Abstract: 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 delay value is based on at least one previous delay value and a current input sample. The transform unit is adapted to calculate a first energy value based on at least a subset of the first plurality of delay values. The gain control unit is adapted to determine if a selected delay value of the first plurality of delay values exceeds a predetermined threshold and scale the selected delay value, the at least one previous delay value used to calculate the selected delay value, and subsequent input samples received after the current input sample by a first amount in response to the selected delay value exceeding the predetermined threshold.

Abstract: Reverberation imparting functions as are obtained by a mechanical type reverberation apparatus employing coil spring delaying elements are simulated by an electric circuit configuration. Three delay loop circuits are individually provided, each including a first and a second delay circuit and delaying and circulating an input signal to thereby simulate the propagation of vibrations through each individual coil spring. Multiplier circuits are provided to individually supplying the out puts from the first and the second delay circuit in one delay loop circuit to the input sides of the second and the first delay circuit in two other delay loop circuits after controlling the signal characteristic to thereby simulate the propagation of vibrations through the supporting plates for the coil springs.

Abstract: An echo canceller (110) for a full-duplex communication system (100) such as a speakerphone determines a gain factor to be used in sub-band adapter coefficient updates by using both time domain and sub-band signals to determine the state of the system (100). In one embodiment a gain factor controller (120) uses the sampled time domain signal to determine if the system (100) is in the silence state, and if not uses the sub-band signals to determine whether the system (100) is in the talk, double-talk, or listen state. The gain factor controller (120) selectively changes the gain factor and selectively performs coefficient updating based on the state. In another embodiment the gain factor controller (120) determines the state and selectively updates coefficients using state information developed on a band-by-band basis.

Abstract: A method of detecting a DC offset in an audio signal provided by an audio processing unit to an audio power amplifier, wherein the audio amplifier provides a clip detect signal back to the audio processing unit, wherein the method comprises the steps of sampling the clip detect signal to determine if the clip detect is active. Detecting a power level of the audio amplifier if the clip detect is active. Next, comparing the power level to a predetermined power threshold. Then, identifying a dc offset if the power level is less than the predetermined power threshold.