Abstract: The disclosure relates to a four conductor circuit arrangement providing two communication channels between a control unit and a terminal device. Power feed and bi-directional signalling are accomplished simultaneously over the same four conductors used for the two commmunication channels without interference. The signalling from the control unit to the terminal is accomplished by means of a voltage modulator circuit in the control unit by which voltage pulses are transmitted via a phantom circuit arrangement over the four conductors to the terminal unit. The voltage pulses are sensed from the phantom circuit in a data receiver which is located at the terminal unit. Connected to the phantom circuit in the terminal unit is a voltage regulator circuit which receives power from the control unit via the four conductor phantom circuit interconnecting the control unit and the terminal. In series with the voltage regulator circuit is a constant current sink and an inductor.

Abstract: An apparatus comprising a stopband filter, a linear amplifier, a limiter circuit, a narrow band filter and a threshold circuit, insensitive to voice signals. When signalling signals are emitted with two frequencies, the apparatus comprises two channels each of them being protected by an input reject filter against one of the signalling frequencies.

Abstract: A telephone station set has subscriber-interface elements associated with rotatable panel (11). Rotatable panel (11) is adapted to serve as a sunshade visor in an automobile. In panel (11), exterior cavity (14) readily accommodates handset (16) in either of two hangup positions. Handset (16) is compact and nonsymmetrical while the interior of cavity (14) completely contains the handset in either of the hangup positions. This arrangement provides the convenience of one handed operation by either hand of an operator. Coiled handset cord (27) emerges from a centrally located port (28) to provide the electrical connection compatible with this convenient operation.

Abstract: The disclosed signal limiting circuit is bridged on to a bidirectional communication path (T, R) and functions to selectively attenuate excessive signals (2V.sub.A) being transmitted in a predetermined direction on the bidirectional communication path. This is accomplished by a signal discriminator circuit (100) which separates the excessive signal (2V.sub.A) from the plurality of signals appearing on the communication path (T, R). The signal discriminator circuit (100) also inverts the isolated excessive signal, passes it through an attenuator (102) to a signal injection circuit (103) which injects a controlled amount of the 180 degrees out-of-phase isolated excessive signal back on the communication path (T, R) to cancel out a portion of the excessive signal, thereby providing selective attenuation of the excessive signal.

Abstract: A system is disclosed for automatically reducing reverberation in typical voice telecommunications systems. This system uses center clipping levels adaptive to the level of reverberation input speech. In one configuration, the voiceband is divided into two sub-bands and center clipping occurs only for the lower band; costs are reduced with surprisingly little transmission quality sacrifice. Clipping-level holdover circuitry with exponential decay appears to work well for a large variety of reverberant enclosures.

Abstract: Disclosed is an echo suppressor circuit which provides a variable loss in a speaker's transmit path, which loss is a function of the relative speaker volumes. The loss provided in the path of a particular speaker is relative to the volume of the speech emanating from each speaker. In one embodiment, the amplitude of the incoming signal is reduced by an amount which is a function of the ratio of the amplitude of the incoming signal to the amplitude of the outgoing signal. Because loss is introduced into a distant speaker's transmit path rather than into his return path, it is possible for a near speaker to break into a conversation before the distant speaker has concluded. Further, since the loss provided is a function of the relative volumes of both speakers with respect to one another, the total loss introduced into the system is minimized.

Abstract: A hybrid bridge circuit has a feed amplifier and an auxiliary resistor connected in series with the output of the receive amplifier between the amplifier and a node of the bridge so that signals from the receive amplifier are transmitted through the two-wire line port in the bridge to the auxiliary resistor and a resistive leg of the bridge, and signals from the two-wire line are transmitted to both the node V1 between the two-wire line port and the adjacent resistive leg of the bridge and the node V2 between the compensating network in the bridge and the adjacent resistive leg of the bridge. A differential transmit amplifier differentially receives inputs from the nodes V1 and V2 so that the differential amplifier produces a partially equalized output signal corresponding to the difference between the voltages at the nodes V1 and V2. The resistance values R1 and R2 of the two resistors legs of the bridge, and the impedances Z.sub.c and Z.sub.

Abstract: A telephone handset is formed from two elongate hollow concave parts, joined at their peripheries, with a circular recess at one end of the lower part. A transmitter assembly is positioned in the recess and comprises a transmitter, a cup-shaped member positioned on the back of the transmitter and a resilient tubular member surrounding the transmitter and at least the lower or front part of the cup-shaped member. The tubular member has a radially inward projecting rim at its front or lower end extending over the front of the transmitter and a similar rim at its rear end engaging over a projection on the cup-shaped member. The resilient tubular member retains the transmitter and cup-shaped member together, and acoustically seals them together and also acoustically seals the front of the transmitter to the base of the recess.

Abstract: A base plate for a telephone set is molded of plastic instead of being a metal stamping and can be made of recycled scrap plastic material. The base plate is provided with a plurality of positions for mounting telephone set parts with each position having an arrangement of projections and one or more deflectable members whereby the telephone items can be mounted by sliding and downward movement to clip in, and with one or more of the positions also having alternative means for mounting items whereby alternate forms of an item can be interchangeably mounted.

Abstract: Digital echo canceler for a modem for data transmission by means of phase and, possibly, also amplitude modulation of a carrier, the ratio between carrier frequency f.sub.o and modulation rate 1/T having the form P/Q, P and Q being integers.The echo canceler receives the binary data to be transmitted for generating an echo copy signal. An echo canceler of a simple implementation is obtained in that the echo canceler comprises means responsive to each symbol configuration at each instant iT for generating at least a number depending on the amplitude allotted to the carrier at said instant iT and for applying this number to at least a given section of an assembly of adaptive digital filter whose output signals are combined for forming a digital version of the echo copy signal, the coefficients of these filters being adjusted by an assembly of adjusting circuits receiving said error signal in digital form and arranged for minimizing a predetermined function of said error signal.

Abstract: A telephone transmission system has repeaters spaced along both the transmit and receive legs of the transmission line, with a power supply for the repeaters including a current regulator having positive and negative supply lines connecting the power supply to the two legs of the transmission line. Current surge protectors are connected from the two legs of the transmission line to ground. A pair of current sensors responsive to the current levels in the positive and negative supply lines, between the power supply and the current surge protectors closest to the power supply, produce output signals representative of the respective current levels. A control signal generating means receives the output signals from the current sensors and produces a control signal in response to a deviation of the higher current in the supply lines from a preselected reference level. The control signal is supplied to the current regulator to maintain the higher current level in the supply lines at the preselected reference level.

Abstract: A mounting apparatus for communication signals exchange equipment is described. The apparatus includes supporting poles, each of which is erected close to each of the components of the communication signals exchange equipment, and further includes frameworks which are assembled horizontally above said supporting poles and rigidly fixed to the top ends of said supporting poles. The supporting poles and frameworks are provided both for mechanically supporting said components and for distributing a large number of communication signals cables between one component and other components. The construction of both the supporting poles and frameworks is completed by the time said components are located at their desired positions.

Abstract: The system receives subscriber station address information in the form of frequency coded tone signals transmitted from a calling station along a common intercom circuit, and selectively accesses a called subscriber station having a corresponding station address in order to produce a call indication ring-out thereat. The system is comprised of decoder circuitry including a digital multi-frequency tone detector for receiving and decoding station address information transmitted from a calling station, and access circuitry operatively associated with the tone detector for routing an appropriate call indication signal to the called station. Signals which appear at the output of the tone detector are delivered to the access circuitry which, in turn, initiates the call indication sequence and routes additional signals back to the tone detector for controlling it during call indication.

Abstract: The invention relates to transmission systems and in particular to level regulators controlled by a pilot tone and used in such systems to correct variations over a period of time in the attenuation of the transmission system.The subject of the invention is a level regulator governed by a pilot tone whose gain control circuit locks in a mean position where there is a very low or zero value detected for the pilot tone. This locking is achieved by modifying the supply voltage of the error amplifier of the loop providing automatic gain control for the regulator.The invention is of particular application to cable transmission systems with repeaters.

Abstract: A telephone set for use in a vehicle having a handset housing with a cramp-like shape with a transmitter microphone on one end and a receiver on the other end, and a detachable dial plate for dialing on the dorsal part of the handset housing approximately behind the receiver. Said dial plate has a groove on either side that fits in with the projection provided on the handset housing. The handset housing has a pin for securing the dial plate, which has a hole for receiving the pin. The arrangement of the pin and the hole provides plug-in facility of the dial plate in the handset. A driver of a vehicle can handle the telephone set with a single hand.

Abstract: The amplifier includes an audio signal input means and a first pair of integrated circuit audio power amplifiers each having an inverting input and a non-inverting input. The inverting input of one of the first pair of amplifiers is coupled to the input means and the non-inverting input of the other of the first pair of amplifiers is coupled to the input means. A first load has one terminal coupled to the output of one of the first pair of amplifiers and the other terminal coupled to the output of the other of the first pair of amplifiers. A second pair of integrated circuit audio power amplifiers each having an inverting input and a non-inverting input. The inverting input of one of the second pair of amplifiers is coupled to the input means and the non-inverting input of the other of the second pair of amplifiers is coupled to the input means.

Abstract: A system for limiting the instantaneous value of a noise transient, by means of an electronic circuit wherein the amplitude of the total input signal being monitored is compared with a threshold value which is varied continuously according to the peak carrier signal value, and the output signal is maintained below the threshold value.

Abstract: An identifier circuit for connection between a telephone system party line and a party line subscriber to permit identification of a calling party line subscriber with automatic number identifying equipment at a central office.

Abstract: A modulated RF carrier signal distributing arrangement, utilizing existing line circuits, is disclosed for providing entertainment signals to key telephone lines in the active noncommunicating (hold) state. The disclosed system utilizes an existing option connector on the line circuit for connection of a music receiver circuit. A centrally located transmitter circuit frequency modulates its own RF carrier with an externally supplied music signal and is wired to the existing common dc power to distribute the modulated RF signals to the receiver via the option connector on each line circuit. The receiver circuitry demodulates the RF signal and couples the resulting music signal directly across the hold bridge leads of the associated line.

Abstract: A telephone network protective coupler for connecting terminal equipment to a telephone central office by means of a telephone line. The coupler includes two hybrid circuits which are interconnected to form a transmitting path and a receiving path. A power limiter in the transmitting path can be programmed remotely by selection of an external programming resistor without the direct introduction of noise into the transmitting path. The programming feature permits the gain of the transmitting portion of the device to be varied in steps from 0 to -12dB., and the maximum power output to be varied correspondingly in steps from 0 to -12 dBm. in order to arrive at an optimum signal power level of -12dBm. at the central office. The power limiter includes a controller gain amplifier for varying the attenuation of the transmitting path to a.c. signals, a remotely adjustable attenuator connected to a d.c.