Abstract: A circuit arrangement is provided for suppressing periodic or non-periodic noise voltage components which are superimposed as an undesirable influence on the DC voltage signal to be evaluated on DC fed, two-conductor transmission lines, particularly for extension circuits in telephone systems which are fed in the subscriber circuit of the exchange location via symmetrical branches and evaluated with respect to the subscriber's loop state changes. By coupling to suitable circuit points of the subscriber circuit, the superimposed noise signal is separated by a differential amplifier and fed to a second differential amplifier. The original loop signals, superimposed with noise, is also fed to an input of the second differential amplifier so that a noise-free useful signal indicating the operational state arises at the output of the second differential amplifier.

Abstract: An audio receiver or other electronic device having a number of controllable functions is provided with control apparatus in which mechanical parts have been substantially eliminated. An electrically controllable device is provided to control each function. Memory registers provide inputs to the electrically controllable devices. The controllable functions may be on-off, as for a particular signal source, or may be variable, as for volume, tuning and tone in a receiver. Input controls include a single level control for adjusting the levels of all of the variable functions, and switches to select the function to be adjusted. Control means such as a microprocessor scans the switches and level control for changes in level and/or functions selected and updates the memory registers accordingly. A display is provided of selected functions and level.

Abstract: The invention relates to automatic outgoing and incoming channel balance and separation circuits between local telephone set lines and network junctors. The separation circuit associated with the telephone set lines possesses an electronic line feed circuit and a separator constituted by an operational amplifier whose output is connected via two equal resistors in series to one of the outputs of the electronic supply circuit, the junction of these two resistors being connected to the output of this separation circuit. The separation circuit associated with the junctor possesses two input amplifiers connected to the network via output resistors of equal value, one terminal of one of these output resistors being connected via a passive resistive and capacitative network to an operation amplifier, and the other terminal of this resistor being connected via a single resistor to this operational amplifier.

Abstract: A frequency selection circuit which is equivalent to an LCR series resonant circuit, though not provided with inductance and which can adjust resonant frequency, selectivity or quality factor Q and circuit impedance at resonance independently of one another, merely by adjusting resistance. The circuit comprises an operational amplifier connected to receive an input signal at its noninverting input, a band rejection filter connected to an output of the operational amplifier, a positive feedback resistor connected between an output of the band rejection filter and the noninverting input of the operational amplifier, and a voltage divider connected between the output of the band rejection filter and the output of the operational amplifier and connected at its output to an inverting input of the operational amplifier. The band rejection filter comprises a series combination of a first resistor and a first capacitor and a parallel combination of a second resistor and a second capacitor.

Abstract: A telephone set base, for both wall and desk top mounting, has an elongate plastic molded base plate and a top housing. To improve stability a flat metal weight is positioned on the base plate and is spaced a small distance from the base plate to form an acoustic chamber. A speaker is mounted on the weight. A printed circuit board is mounted over the weight and modular jacks are attached to a flexible circuit member which connects to the printed circuit board, speaker, and other items. Recesses are formed in the base plate to provide for alternative arrangements of line cords and plug-in mounting on a wall. Slots in the base plate provide access to the recesses for cords entering at the ends of the base plate. A battery housing is provided.

Abstract: For a telephone handset, a rigid chassis is provided, of elongate form with positions at each end for mounting respectively a receiver and a transmitter and an intermediate position for a pushbutton dial. A flexible circuit member carries the majority of the various components for the handset. The flexible circuit is elongated and extends along the back of the chassis, down through a slot and back along the front of the chassis, with the pushbutton dial assembly attached to the flexible circuit member. The majority of the items such as electronic components, recall button, line cord jack and other components can be preassembled to the flexible circuit member which is then assembled to the chassis, followed by attachment of the pushbutton dial assembly.

Abstract: A conventional interface for 2-wire telephone lines to a digital switch includes line current feed resistors and a bridge circuit where the line impedance is compared with a compromise balance network. The accuracy of the balance determines the proportion of the signal received on the receive pair being retransmitted in the transmit direction. The ratio of these signals is known as the Trans-Hybrid loss and should be as high as possible for good quality speech.In practice the telephone line impedance increases with length as also does the DC resistance of the line and thus the line current, assuming a constant voltage source.It is proposed that the line current feed resistors be formed on a common substrate using well-established film deposition techniques and the balance resistor be formed on the same substrate using a material having a negative temperature coefficient.

Abstract: A device for developing a neutralization signal for an echo suppressor is required for the transmission of data over a telephone line having four-wire circuits. Each transmission of data is preceded by an identification signal at a given frequency. An input analog signal including the identification is sampled and quantized so that each sampled value is encoded into a binary codeword composed of a sign bit and a preset number of bits representing the magnitude of the analog signal. The device includes a detecting circuit to detect the identification signal, a level assessing circuit to assess the level of the codeword sequence, and a hangover circuit responsive to the detecting circuit and the level assessing circuit to develop the neutralization signal. The detecting circuit includes a bit pattern generator which produces successive bit patterns from sign bits of the codeword sequence.

Abstract: A transmission bridge comprising two alternating current circuits having a non-inverting signal input, an inverting signal input and a signal output, the non-inverting signal inputs being coupled to associated connecting terminals for the connection of a subscriber's line, the inverting signal inputs being connected to those terminals to which the non-inverting signal inputs of the other alternating current circuits are coupled, the outputs being coupled to the connecting terminals via supply resistors for preventing the anti-phase signals such as speech signals, present at the terminals, from being attenuated and for attenuating by means of the supply resistors in-phase signals, such as noise signals induced in the subscriber's line, present at the terminals.

Abstract: The two talking wires of a line loop extending from a subscriber station to a central office, provided with respective blocking capacitors, are connected on the subscriber side of these blocking capacitors to respective signal detectors fed from a common battery and cross-coupled by a common compensating capacitor. The two signal detectors receive outgoing signals from the central-office equipment via a common photoelectric coupler and transmit incoming signals to that equipment by way of respective bistable threshold comparators and individal photoelectric couplers. The two signal detectors with their threshold comparators are constituted in integrated circuity by mutually complementary transistors and diodes together with associated resistors.

Abstract: A four-transistor bridge amplifier is adapted for use as a bidirectional speech amplifier between a telephone line and an electronic telephone subscriber's instrument. The amplifier is powered from the line and includes two-transistor sections, one or other of which functions dependent on line polarity. The output of the amplifier to the subscriber instrument is taken across a resistor connected between the transistors such that the output always has the same relative polarity whatever the line polarity.

Abstract: A processing device transmits speech signals of constant amplitude during periods of voice activity and interrupts transmission outside these periods, so that noise is not transmitted. To this end the processing device comprises an amplitude-compressing device preceded by a voice activity detector comprising a delay line in series with an electronic switch and a speed - noise discriminator having a common input with the delay line for receiving the voice signals. The switch is controlled by the output signal of the discriminator in such a way that it only permits the passage of the voice signals corresponding to the periods of voice activity.

Abstract: An adaptable telephone baseplate can be used for either wall mounting or desk or table top mounting. The baseplate has an enclosed recess at an intermediate position and a modular jack position at what would be the top edge when wall mounted. A slot connects the jack position and enclosed recess. When wall mounted a short cord can be inserted in the slot with a plug at one end being inserted in the jack at the jack position and a plug at the other end being in the recess for insertion into a wall jack. When desk mounted a normal line cord enters through a groove into the jack position for insertion of a plug into a jack. Alternatively a line cord can enter through the groove, extend along the slot and then pass up through the slot for hard wiring of the conductors to a circuit board. Snap-in mountings are provided for the jack, a circuit board, ringer and possibly other items.

Abstract: An adaptive hybrid circuit for connecting two-wire and four-wire telephone transmission lines to minimize singing, oscillation or echoes due to impedance mismatch. The circuit comprises a variable impedance circuit connected between the two-wire and four-wire circuits. In one embodiment one end of the variable impedance circuit is connected to the two-wire circuit and to one input of an adder to which the reception signal from the four-wire circuit is also applied and compared in reverse phase and half amplitude. The resulting transmission signal is used to adjust the variable impedance circuit so as to minimize the transmission signal. In another embodiment the variable impedance element is connected to an impedance through which the four-wire reception signal is applied and is further connected to one input of an adder which compares this input in reverse phase with the two-wire signal to produce a transmission signal.

Abstract: A device for freeing an area of birds, insects, or other pests which simultaneously emits two separate audio frequencies which are shifted periodically. The device comprises two separate oscillators whose output signals are mixed together at the input of a power amplifier driving a loud speaker. The frequency of each oscillator can be independently adjusted. A resistive load is placed in the common power supply line of the two oscillators and is periodically shunted in order to shift the frequency of both oscillators. The periodical shunting of the load is accomplished by a SCR switch driven by a third oscillator having a very low frequency. The resulting dual frequency pulsating signal can be adjusted with wide ranges of frequencies in order to deter various types of animals from frequenting the area.

Abstract: An improved current source circuit is adapted for use with two-wire transmission systems of the type encountered in telephony, and has excellent common mode noise rejection. In its various embodiments, the current source provides an interface for coupling signals with a telephone pair, operates to cancel or negate the effect of unwanted impedances on the pair, generates a selected impedance across the pair, and functions as an electronic hybrid circuit for interfacing between a two and a four-wire telephone transmission facility, all while affording common mode rejection to noise on the line. In addition, the various embodiments of the current source are combined into an improved terminating set for a two to four-wire telephone transmission facility.

Abstract: A residual echo suppressor for an echo canceller compares the levels of the uncancelled signal and the residual signal. If the level of the residual signal has a selected proportionality to the level of the uncancelled signal, it is assumed that the residual signal consists solely of echo and it is suppressed to zero. If the residual signal fails the proportionality test, which indicates that it may contain speech, it is transmitted in its entirety. To prevent sporadic transmissions of residual signal which fails the proportionality test, but which might not contain speech, a hysteresis circuit blocks transmission of the residual signal upon the same continuously failing the proportionality test for a selected time, at the end of which time the residual signal is assumed to contain speech and is transmitted.

Abstract: A filter network is interposed between an audio amplifier and a speaker system consisting of a woofer, midrange and tweeter. The reactive elements for the filter sections associated with the woofer, midrange and tweeter, respectively, are interrelated by mathematical formulas and there is a capacitor lock connected across the input terminals of the network. The value of the capacitor lock is mathematically related to the values of the reactive elements to achieve superior overall performance for the speaker system. The filter or crossover network is designed for matched or unmatched speakers. This design uses a frequency system based on F.sub.1, F.sub.2 =8F.sub.1 and F.sub.3 =16F.sub.1, where F.sub.1 is a selected frequency in the lower portion of the audio spectrum.

Abstract: A digital logic circuit for eliminating spurious transient pulses (21, 32) from among genuine pulses (51) in a binary dial pulse stream. The dial pulse stream is coupled to the circuit input (46). Output (47) is prevented from matching the input unless the duration of the input change exceeds a first time interval (57). Moreover, if the input change exceeds the first time interval and the input change was from a first to a second predetermined binary signal, then the new output signal is held constant for a second time interval (56) regardless of any change in the input signal.

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 (RKN, RZN, etc.) of an impedance network (202, FIG. 3, FIG. 4) to obtain an optimum match to the impedance of the bidirectional facility (102). To this end, individual ones of a plurality of tones (107) are supplied to a receive port (111) of the transmission network (101) and the impedance elements (RKN, RZN, etc.) are controllably adjusted in a prescribed sequence (FIGS. 8-16) to obtain amplitude nulls at a transmit port (112) of the transmission network (101). In one embodiment, predetermined ones of the impedance adjustments (RKN, RZN, etc., 820-823, 828-831) are iterated with predetermined ones of the tone signals being supplied to the receive port (111) further to optimize the impedance match.