Abstract: A remote volume control for television sets wherein an unshielded flexible metal shaft is directly connected to the television volume control at one end and at the other to a motor driven gear train mounted to the side or top of the set adjacent to the volume control. Remotely positioned hand-held switching means and batteries permit the user to effect clockwise and counter-clockwise rotation of the volume control shaft to control volume.

Abstract: A two-way amplifier arrangement which automatically controls current flowing in the transmission circuits to maintain that current at a fixed level. The two-way amplifier arrangement finds utility as a conference amplifier and as a two-way trunk amplifier.

Abstract: An electronic hybrid for coupling a two-wire line to a four-wire line and having a two-wire port adapted to be connected to the two-wire line, separate receive and transmit ports adapted to be connected to said four-wire line, means for coupling signals received at said two-wire port to said tramsmit port, and a circuit connected to said receive and two-wire ports and including a pair of constant current sources for driving the two-wire line that is connected to said two-wire port in response to a signal imposed on said receive port.

Abstract: PCT No. PCT/SE 78/00061 Sec. 371 Date June 24, 1979 Sec. 102(e) Date May 31, 1979 PCT Filed Oct. 18, 1978 PCT Pub. No. W079/00227 PCT Pub. Date May 3, 1979A fastening arrangement for one or more circuit cards in a telephone instrument having a housing comprising a base plate with walls around the perimeter of the housing extending substantially perpendicular to the base plate and a rear casing which has a planar surface extending perpendicular to the base plate and directed towards the front of the instrument. Supporting elements are mounted on the planar surface and have the form of projections with grooves to receive a circuit card. The front wall of the base plate carries supporting elements for the circuit cards.

Abstract: An automatic gain repeater for varying the amplification of AC signals transmitted through a telephone subscriber loop in accordance with the impedance of such subscriber loop is described. The automatic gain control circuitry includes controllable variable gain amplifiers connected in series circuit arrangement with the subscriber loop. The gain of the amplifiers is varied, in a continuous manner, in accordance with the subscriber loop line impedance such that the overall transmission line loss is a constant predetermined value. Gain of the amplifiers is accomplished by means of a control signal generated in a loop extender circuit that is coupled to the subscriber loop.Impedance networks coupled to gain repeater hybrid transformers provide minimum operating power loss with maximum power transfer between the automatic gain repeater circuit and subscriber loop while maintaining adequate transhybrid loss between the two directions of transmission and matching input impedance.

Abstract: The output derived from an electric circuit such as an OCL type power amplifier circuit is delivered to a load such as a speaker, through a switching means such as a relay. When the operation of the electric circuit has come out of a predetermined range of operation, the switching means is operated to break the connection between the electric circuit and the load. A detection circuit for detecting the operation of the electric circuit includes a detecting transistor constructed in a semiconductor integrated circuit. The detecting transistor is connected at its base to the input terminal for external connection of the semiconductor integrated circuit, so as to receive a signal representative of the operation state of the electric circuit. The detecting transistor is so biased as to allow a predetermined electric current to flow therethrough, when the electric circuit is operating within the predetermined range of operation.

Abstract: A circuit and method for controlling the connection of a cancellation network between the four-wire input and output of a hybrid transformer at the two-wire to four-wire interface of a telephone line. The relative phase of a signal applied to the four-wire input appearing on the four-wire output, is used to determine whether the two-wire telephone line appears loaded or non-loaded. This in turn controls the selection of the appropriate cancellation network which will give the greatest singing return loss.

Abstract: Transhybrid loss is maximized in a transmission network (FIG. 1, 101) of the type for coupling a bidirectional transmission facility (102, 2-wire) to receive (103) and transmit (104) unidirectional transmission facilities (4-wire) by automatically adjusting impedance elements (RKL and RZL) of an impedance network (202, FIG. 3) to obtain an optimum match to the impedance of the bidirectional facility (102). To this end, a plurality of tones (107) are individually supplied to a receive port (111) of the transmission network (101) and the impedance elements (RKL and RZL) are controllably adjusted in a prescribed sequence (FIGS. 7-10) to obtain amplitude nulls at a transmit port (112) of the transmission network (101). Then, an additional signal having a plurality of predetermined frequency components which repeat periodically is supplied to the receive port (111) and a predetermined one of the impedance elements (RKL) is again adjusted to obtain an average value amplitude null at the transmit port (112).

Abstract: Subscriber line interface circuit for connecting a subscriber's telephone line to, for example, an automatic telephone exchange comprising a pair of amplifiers whose outputs are connected to the wires of the telephone line and which are fed by a d.c. voltage supply source. This supply source provides the telephone line with direct current via the amplifiers. In practice, the telephone line must be terminated by a symmetrical impedance of a prescribed value. To this end the interface circuit comprises means for determining the weighted sum of the current flowing through one and through the other wire of the telephone line such that the sum current is independent of the longitudinal currents in the telephone line. By means of an impedance, two antiphase feedback voltages are generated at the inputs of the amplifiers, these amplifiers then having a symmetrical impedance at their outputs.

Abstract: An automatic equalizer for digital transmission systems is disclosed including a variable gain amplifier in one branch of a two-branch admittance circuit. The branch including the amplifier includes two frequency-dependent admittances while the other branch is insensitive to frequency. Varying the gain of the amplifier provides a minimum phase network which can be automatically adjusted to compensate for varying lengths and gauges of telephone pairs. This configuration permits digital transmission in the subscriber loop plant at rates up to 200 kilobits per second.

Abstract: The optical viewing device described comprises, in combination, an optical viewing tube for securing through the thickness of the door, an "outside" unit for attachment to the outside of the door and engaging around one end of the optical tube and an "inside" unit for securing to the inside of the door around the other end of the viewing tube, the "inside" and "outside" units including an audio microphone/speaker device to enable a caller audially to identify himself and the outside unit including a self-contained lighting unit to illuminate a caller. With such a device, a person inside the door can determine the identity and purpose of a caller before opening the door.

Abstract: An electronic circuit simulates the direct current characteristics of the hybrid transformer portion of the telephone system call-handling equipment. The circuit is connected across a two-wire telephone subscriber loop and supplies a loop current that is proportional to the difference between a constant current and a reference current. The circuit contains a voltage sensing circuit which senses the voltage across the loop and transfers the sensed voltage across a reference resistor, thereby developing a reference current through the resistor which is proportional to the voltage across the subscriber loop. An integral current generator supplies a constant current to the circuit. An integral current subtractor, connected between the output of the voltage sensing circuit and the current generator subtracts the constant current from the reference current. The resulting current forms the input current to an integral current amplifier.

Abstract: The present invention discloses an adaptive digital echo cancellation circuit including a finite impulse response digital filter, wherein the digital filter coefficients are adapted by continuous updating to compensate for telephone subscriber line echo conditions to enable the digital filter to continuously simulate the instantaneous subscriber line echo. The continuous coefficient update is provided by a correlator which includes provision for introducing non-linearities into the PCM transmitted and received signals, in parallel with the speech path, to derive a simplified digital representation of the PCM speech, thereby reducing the signal processing hardware required by the correlator to derive the updated filter coefficients.

Abstract: A control unit for establishing a four-wire connection between two terminals via a pair of telephone lines comprises switching means which are operable to provide a connection to a pair of telephone lines, signalling means connectible to said lines via said switching means to enable another control unit to be signalled via a line, and line send and receive circuitry connected to the switching means. The line send and receive circuitry has an input for connection to the send channel of a terminal and an output for connection to the receive channel of the terminal. A central control controls operation of the switching means and line send and receive circuitry to automatically establish a four-wire connection and adjust parameters of the line send and receive circuitry to compensate for loss on the telephone line.

Abstract: A system is disclosed for processing speech signals to enable effective power increase in a device utilizing the said signals. The system includes means for filtering an AF electrical signal analog of the speech signal, to thereby provide an AF signal including a narrow passed band of frequencies. The output from the filtering means are provided to means for symmetrically clipping the said output, to provide a series of pulses of constant amplitude, the discontinuities of which coincide with the zero axis crossings of the original AF signal. Sufficient amplification is provided at the filtering means to assure that the signal proceeding to the symmetrical clipping means is of sufficient amplitude in relation to the clipping level to enable the foregoing result. Reshaping low pass filter means receive the output from the symmetrical clipping means and sinusoidally reshape the said pulses.

Abstract: A circuit which is particularly adapted for reconstructing fixed time duration dialing pulses in a telephone communications system while rejecting spurious pulses of less than a selected pulse duration. The circuit utilizes two coupling networks having integrated outputs of opposite polarity which are summed after passing through two separate switching amplifiers. The summed outputs are fed through a third switching amplifier having a hysteresis characteristic so that it switches only when both outputs have switched to the same polarity.

Abstract: A connecting block for telephone systems comprises insulating supports carrying input and output terminals for connecting the wires of the telephone lines. It comprises a case provided with guides cooperating with ribs formed on insulating plates. Each insulating plate carries on its inner face one input terminal and one output terminal. Each input terminal has an extension which, in the inoperative condition, contacts an extension of the corresponding output terminal. Channels are formed on the plate for facilitating the insertion of the wires having their ends connected to the input terminals, the same applying to the output terminals.

Abstract: A telephone set which is provided with extra space normally intended to accommodate additional communication equipment such as, for example, loud-speaking equipment. A storage box, preferably rectangular and made of plastic, is inserted into said extra space, the components, circuit cards, etc. then being sealed off from the telephone user. The box can, for example, accommodate a roll of paper and is provided with a cover and longitudinal grooves, the paper running in the grooves and forming a writing surface for the user.

Abstract: The present invention discloses a reduced power dissipation telephone subscriber line feed circuit in which the battery feed current from the central office is determined by the subscriber loop resistance for medium to long loops, and for shorter loops, for which the battery feed current would exceed a given predetermined threshold, the feed current is limited to the threshold value. The invention also relates to compensation for loop and subset attenuation characteristics.During operation in the current limited mode, attenuation is automatically inserted into the signal transmission and receiving paths in order that normal equalizer operation will not be impaired by current limiting of the battery feed current. A multiple telephone subscriber system is disclosed wherein the circuitry used in deriving current limiting control signals is shared in a multiplexed arrangement by a plurality of subscriber lines.

Abstract: A closed sound delivery system includes a sound generating unit coupled to provide sound to an ear in response to electrical input signals and an electrically equalized sound receiving unit coupled to accurately receive acoustical signals provided by the sound generating unit in the vicinity of an ear. The delivery system provides a pressure at the eardrum with a frequency response which remains flat up to about 30 KHz. The sound generating unit includes a low acoustical output impedance transducer and a suppressor element which attenuates acoustical energy emanating from all but a small central region of the transducer to minimize frequency response variations resulting from constructive and destructive interference of acoustical energy originating at different physical positions. The receiving unit has a 6 dB per octave high frequency roll off due to the characteristics of its terminating elements while an electrical high pass filter compensates for this roll off.