Abstract: A telephone handset outbound noise canceller uses an omnidirectional reference microphone placed near the transmitter grille. Two adaptive filters are employed, one driven by the handset transmitter to subtract speech from a reference value to produce an enhanced reference signal; and a second adaptive filter driven by the enhanced reference signal to subtract noise from the transmitter. The weights of the two adaptive filters are allowed to adapt or are frozen according to criteria set as a result of transmitter power measurements which determine whether speech is likely to be present or not.

Abstract: A two-wire termination impedance generation circuit of a subscriber circuit including differential amplifiers, which is provided with a network circuit including capacitors and resistors, an input point, and current sources, the capacitor being comprised of series connected first and second capacitors, the resistor being comprised of series connected first and second resistors and having a high band bypass capacitor connected at the intermediate connecting point of the same, and the resistor being comprised of a complex termination resistor forming an internal termination impedance and a series connected complex termination resistor and complex termination capacitor being connected directly to the telephone line as an external termination impedance, wherein the frequency characteristics can be improved in three ways.

Abstract: A white noise suppressing circuit for suppressing white noise contained in a received voice of a speaker telephone apparatus includes a filter for suppressing white noise contained in an aural input signal input to an aural signal line, a switch for short-circuiting the filter, a detecting circuit for detecting the aural input signal, and a comparator for comparing an output of the detecting circuit with a preset voltage and for controlling the switch on the basis of the results of the comparison. When it is determined by the comparator that there is a voice input, the switch is short-circuited to make the filter inoperable. When there is no voice input, the switch is opened so as to make the filter operate.

Abstract: In a computer network having a cable for transmission of electrical signals between data terminal equipment and a device used to control and route data in the network, an apparatus for terminating the cable to minimize emissions radiating from the cable and susceptibility of the cable to outside interferences. The cable is comprised of unshielded twisted pairs of wires. Each twisted pair is individually terminated into a matching input impedance. The difference signals being conducted in each twisted pair produces common mode currents which sets up standing waves through the cable. Consequently, at each end of the cable, the common mode of the twisted pairs is terminated into a load having an impedance approximately equal to the common mode impedance of the twisted pairs. These loads effectively dissipate the energy from the standing waves, thereby minimizing emissions. Reciprocally, susceptibility is likewise minimized.

Abstract: A control circuit for automatic elimination of telephone line noise, a reference tone selecting device for selecting the tone signal on the telephone line; a mode switching device for switching registration of noise pattern and operation of speech transmission; a noise pattern outputting device for outputting and storing frequency spectrum pattern in accordance with noise element coming on the telephone line during the noise pattern registration pattern; and a noise eliminating circuit for eliminating noise element from the transmission signal on the telephone line in accordance with the frequency spectrum pattern.

Abstract: A connecting line is provided between a switching center and a subscriber for transmission of telecommunication signals. At the subscriber's end of the connecting line, there is located a device which, in addition to other passive and active units, includes a transformer, whose output winding is subdivided into two partial windings of identical size. A first capacitor, a switch and a second capacitor are connected in series between the partial windings. To prevent distortions of the dial pulses, a connecting line between the switch and the second capacitor is connected with a reference potential of the circuit arrangement.

Abstract: An apparatus 10 controls the two-way communication between the microphone 12 and speaker 36 of a telephone headset and a telephone base. A transmit channel 15 includes an expander 18 that controllably attenuates the transmitted communication signal when the user is not speaking into the microphone 12. Conversely, a receive channel 30 includes a compressor 34 that controllably attenuates the received communication signal to prevent over driving the speaker 36.

Abstract: A subscriber circuit has, in a subscriber line section thereof an in-phase induced noise suppressing circuit which is made up of two series connections of a capacitor and a non-linear element. When an intermittent high-voltage signal is being propagated on another subscriber loop, the noise suppressing circuit suppresses it to thereby prevent it from being transmitted to terminal equipment as noise. Since the degree of suppression of the in-phase induced noise can be limited as desired, the subscriber circuit is advantageously applicable to terminal equipment or line equipment having a line interface implemented as an LSI integrated circuit.

Abstract: A method and circuitry for reducing noise is provided. The circuit receives a digital data signal at its input (26). The signal is input to a magnitude evaluator (28) and a pass/squelch circuit (30). Magnitude evaluator (28) samples the digital signal and controls an integrator (36) according to the magnitude of each of the samples. Integrator (36) averages the magnitudes over time. If the signal is a noise signal, integrator (36) toggles a switch (40) to activate pass/squelch circuit (30) to squelch the digital data at its input (29). If the signal is a valid signal, then integrator (36) toggles switch (40) to deactivate pass/squelch circuit (30) to allow the digital data to pass therethrough to destination device (44).

Abstract: Filter circuitry for filtering noise from a pair of telephone conductors connected to a modem or a facsimile transmission unit includes a capacitor in series with a fixed resistor. A vaariable resistor is connected in series with the capacitor and the fixed resistor. The capacitor is non-polarized. A switch is connected in series with the filter elements for selectively connecting and disconnecting the filter from the telephone conductors.

Abstract: A longitudinal cancellation circuit for use in circuits providing a received differential signal containing a desired differential component and an undesired longitudinal component has a first multiplier for multiplying received differential signal with the longitudinal signal to produce a first signal having at least a DC component in addition to other frequency components. The first signal is received by a low-pass filter which produces a second signal containing only the DC component. A second multiplier multiplies the second signal with the undesired longitudinal signal to produce a third signal equal to the to the undesired longitudinal component. The third signal is subtracted from the received differential signal to produce the desired differential signal which is free of undesired longitudinal component.

Abstract: The severity of the problems of transmitting high speed data over a regular twisted wire pair are legendary. These problems arise from a variety of conditions, including the capacitance of the wire (which increases with length) and the propensity of unshielded wire to pickup high induced voltages. An arrangement is disclosed that is suitable for short, as well as long, wire distances and which also effectively eliminates the interference problem caused by induced voltages, including those causes by electrostatic discharge. This arrangement passes two twisted wire pairs through a series of ferrite cores. The twisted wire pairs coming out of the ferrite cores are terminated such that one of the pairs is connected to ground while the signal carrying twisted pair is connected to a small signal balun coil, pulse shaping circuit and low pass filter.

Abstract: A terminal station operating with a current supplied from a master station exchanges signals with it through cable conductors, one of the cable conductors being grounded at the master station to allow the current to return from the terminal station. A receive circuit is formed by a first differential amplifier and a first resistor network connected in a balanced relationship to input terminals of the first differential amplifier for receiving a signal from the master station in a noise-cancelling relationship with respect to the ground potential to eliminate the effect of noise generated by the passage of the current through the ground conductor.

Abstract: A telephone handset having a receiver housing at one end has a flux coil positioned at the front corner at the junction between the peripheral wall and the front wall of the housing. The flux coil is connected in series or in parallel with the receiver. The flux coil, by this arrangement, is positioned very close to the front face of the receiver housing, giving very good coupling between flux coil and a hearing aid. Normally unused space is occupied by the flux coil and permits use of any convenient receiver.