Abstract: Echo canceller, canceling an echo signal y (t), generated by a signal x (t), comprising a transversal digital filter whose N weighting coefficients C.sub.i, correlated with N coded samples of x (t) enable the forming of a synthetic echo signal y (t) and comprising an adaptive control loop adjusting the coefficients C.sub.i, characterized in that the adaptive control loops effects the correlation between the signs of the N coded samples of x (t) and of the residual echo signal .gamma. (t) and determines the correction .DELTA. C.sub.i adjusting the coefficients C.sub.i by multiplication of the residual signal .vertline. .epsilon. (t) .vertline. by a coefficient .alpha. close to zero accompanied by the sign of the aforementioned correlation of signs.

Abstract: A telephone line battery feed circuit for supplying talking current to a subscriber subset and at the same time reducing common mode interference signals. The inputs of a differential operational amplifier are coupled to a telephone line and the outputs of the differential operational amplifier are coupled to a battery feed circuit. The battery feed circuit provides talking current to the subscriber subset and the differential operational amplifier presents a high impedance between the battery and the telephone line to differential voice signals while at the same time presenting a low impedance between the telephone line and the battery for common mode interference signals thereby reducing the latter.

Abstract: Apparatus for electrically communicating between a given location and a variably spaced apart remote location, the locations being connected via electrical conductors. A variable gain amplifier is connected in series between the spaced apart locations for variably amplifying the signals communicated therebetween. A gain control signal that is a function of the separation between the locations is generated and applied to the variable gain amplifier to vary the gain of the amplifier in accordance with the distance between the locations. The gain control signal is proportional to the effective resistance of the electrical conductors extending between the locations. The gain of the amplifier is varied by varying the transconductance of a transconductance amplifier connected in the amplifier feedback circuit in accordance with the gain control signal.

Abstract: An echo controller comprises a parallel circuit of an echo suppressor and a self-adaptive echo canceller near an echo path of a long-distance telephone network. The echo controller further comprises a mode switch responsive to levels of a received signal, an unprocessed signal, and an output signal of the echo canceller and operable during absence of double talk for suspending operation of the echo canceller and putting instead the echo suppressor into operation only when characteristics of the echo path and operation of the echo canceller are objectionable.

Abstract: A connection system for varied distance digital communication capable of handling telephone signals utilizes Voice Activity Compression (VAC) to effectively share a given number of digital transmission channels among a greater number of virtual telephone connections. The telephone signals are delta-modulated and demodulated in system connection stations. The VAC processing circuits with a small increment of decision logic provide echo suppression. Echo suppression is thereby rendered as a "value-added" service at a relatively small increment of station cost over the cost of VAC processing. Echo interference with original telephone signal activity in the send channels is reduced by digital control of gain in the demodulation stage. The system also provides connections without VAC handling subject to echo control.

Abstract: Apparatus for powering a signal amplifier or repeater connected to the primary or high-voltage portion of a power distribution system. Oscillator and amplifier circuits are energized by power from the secondary or low-voltage portion of the power distribution system. The oscillator and amplifier circuits are connected to the primary winding of an air-core transformer. A capacitor is also connected to the primary winding to make the primary circuit of the air-core transformer resonant at the frequency of the oscillator. The secondary winding of the air-core transformer is connected to a resonating capacitor and to transformer and rectifier circuits which convert the AC voltage into DC voltage for powering the signal amplifier. Electrical isolation between the high-voltage and low-voltage portions of the distribution system is provided by the separation distance between the primary and secondary windings of the air-core transformer.

Abstract: A circuit arrangement to enable one party to have a two-way conversation simultaneously with an outside party and an internal party. The circuit arrangement includes circuitry so that the outside party cannot hear anything that is said by the internal party or vice versa. Thus, the one party has the ability to talk to both the outside and the internal party without them hearing each other while using one subset and not putting anyone on hold. In addition, the circuitry includes a button which when depressed enables all three parties to be put into a two-way conference.

Abstract: A direct coupled transformerless hybrid for providing signal conversion between a balanced bidirectional transmission path and a pair of unbalanced unidirectional transmission paths, for providing direct current to the bidirectional transmission path, for suppressing longitudinal mode signals supplied by the bidirectional transmission path, and for providing signal balance to suppress transmission of reflected echoes from the incoming unidirectional transmission path to the outgoing unidirectional transmission path.Of the several embodiments disclosed each includes a plurality of current mirror circuits, some of which include elements of complementary conductivity type to the elements of the remaining current mirror circuits. Each current mirror circuit has a voltage supply terminal, an input terminal, at least one output terminal, and means for supplying a current to the output terminal proportional to the current at the input terminal.

Abstract: An automatic impedance matching network for a transmission line includes an impedance monitor which provides a control signal for two variable compensators. One compensator corrects an impedance mismatch at low frequencies while the second compensates within a higher frequency range. A directional sensor completes a conductive path for the control signal to the variable compensators only for the direction of signal propagation indicative of the impedance of the transmission line being compensated. The disclosed arrangement operates automatically from the intelligence signals transmitted over the line to provide impedance compensation for a variety of cable sizes of different lengths.

Abstract: There is provided a line circuit for connection to a key telephone system for indicating an incoming call, a call placed on hold, and an answered call. There is further provided a means for automatically indicating that the incoming call has been placed on hold for a predetermined time period. There is further provided a solid state device which switches telephone instrument lamp current for visual indication of the various line circuit operations.

Abstract: A modular distribution frame assembly for carrying telephone line terminal and protection blocks in a substantially complete factory-prewired condition. The modular distribution frame has a base for securing to a floor support and a telescopic upper end for securing to an overhead support. The distribution frame assembly has a main vertical open column for receiving the plurality of jumper wires which are used to interconnect incoming subscriber or trunk lines with central office distribution lines. Incoming lines can be introduced into a secondary vertical open column located next to the main open (jumper) column for connection either directly to the appropriate protection or line terminal blocks or to a multiposition connector which has its mating half mounted to and electrically connected to the appropriate protector or line terminal blocks.

Abstract: A circuit arrangement to enable one party to have a two-way conversation simultaneously with an outside party and an internal party. The circuit arrangement includes circuitry so that the outside party cannot hear anything that is said by the internal party or vice versa. Thus, the one party has the ability to talk to both the outside and the internal party without them hearing each other while using one subset and not putting anyone on hold. The circuitry is also provided with a designated button, which when depressed places all three parties in a two-way conference. In addition, the circuitry includes a resistance network coupled between the transmitter and receiver of the one subset both in the outside circuit and the internal circuit associated therewith to reduce sidetones in the receiver of the one subset.

Abstract: Only one reversible electro-acoustic converter is used to act without a press-to-talk switch or the like as a transmitter and a receiver. The electro-acoustic converter is connected to a communication line through two 2 - 4 converters in the form of hybrid transformers which are interconnected to form a transmitting system and a receiving system.

Abstract: The present invention concerns a toy telephone or home intercom in which the electrical parts and connections are prefabricated into a self-contained unit which can be detachably mounted in a telephone case.

Abstract: To prevent clandestine listening devices located in a key telephone subscriber station from utilizing the tip and ring leads of the subscriber station as a transmission path out of the subscriber's building, the subscriber station tip and ring leads are open circuited at the line card circuit during an on-hook or hold condition. Besides isolating the tip and ring leads from the subscriber station during hold and on-hook, the security line card circuit prevents high frequency signals from propagating down the telephone line when the subscriber station is on-hook. The security line card circuit allows the subscriber to exercise full supervisory control over the telephone lines and includes circuitry that controls the operation of audible and visual indicators of the associated key telephone.

Abstract: Disclosed is a line circuit providing the normal line circuit functions and key system control functions within an exchange using time division switching. The line circuit may be used interchangeably for key telephones or non-key telephones. In the former case, the circuit provides the well-known key telephone features for multiple line access at each station of a plurality of stations. Each line circuit provides electronic signalling controls, such as lamp flash indicating a call awaiting an answer, lamp wink indicating a line is on a hold condition, and the fully lit line busy indication, together with audible controls for a called line, and also provides an inverted flash signal at the line circuit for trouble or problem situations.

Abstract: A telephone paging system includes a central interconnect station responsive to phoned information for automatically transmitting the caller's verbal message to a designated portable paging receiver. The central station instructs the caller by means of a prerecorded message to provide a brief voice message preceded by touch tone or rotary dial digits identifying the receiver to be paged. The paging code digits and message are both tape-recorded by the central station. If the transmitter is free, the recorded paging code is automatically played back through a decoding circuit responsive to rotary dial clicks as well as touch tones. The output of the decoding circuit keys a radio transmitter which transmits a corresponding code followed by the recorded voice message. The central station employs a plurality of recorders. If one recorder is in operation, an incoming call is transferred to the next recorder. Recordings awaiting access to the transmitter are taken in a predetermined order.

Abstract: Transmission and signaling range of a telephone transmission line is extended by controllably inserting boost potentials into the line to series aid an applied central office battery. Insertion of the potentials is realized by sensing the direction of current flow in the line and switching a corresponding potential into the line. Optical couplers, each including a light emitting diode and an associated phototransistor, are employed as the line current sensing elements and switching elements.

Abstract: Echo suppressor break-in circuitry must be able to distinguish between double-talking speech on one path of a transmission channel and echos on that one path due to speech on the other path in order that suppression can be removed when both parties are talking. The present disclosure relates to an improved method and arrangement for approximating the echo that may result on an echo return path from speech on another path, which approximation may then be compared with the actual signals on the return path to determine the presence of double-talking speech. In an illustrative embodiment, a first memory store arrangement follows increasing magnitude signals and, during decreasing magnitude signals, provides an output signal corresponding to a predetermined decay rate. A second memory store arrangement follows increasing signals, less a predetermined loss, and holds the magnitude of the last peak while the signal is decreasing.

Abstract: Housing assembly fabricated of a lightweight non-metallic material for housing a plurality of telephone line repeaters. The housing assembly includes a circular base with a perpherial thread, a generally bell-shaped cover, and a threaded retaining ring for securing the cover to the base. The repeaters are mounted in modular chassis in the housing, and the chassis can be stacked to accommodate a desired number of repeaters. Cable assemblies to be connected to the repeaters are removably secured to the base outside the housing, and the cables pass into the housing through sealed openings in the base. Valve means is provided for pressurizing and depressurizing the housing if desired.