Matches 301 - 350 out of 396 < 1 2 3 4 5 6 7 8 >
Match Document Document Title
4593161 Method of initializing a filter in an echo canceller and communication system using said method  
A method of initializing a filter in an echo canceller as used in a telephone system that includes hybrid transformers for connecting unidirectional lines to bidirectional lines and vice versa....
4588863 System for facilitating professional telephone communication  
Improved telephone apparatus. Circuitry in the apparatus includes a memory unit. Telephone numbers can be dialed into the memory unit while an individual is conversing over the telephone. After the...
4578541 Telephone line interface circuit  
An interface circuit for providing power and signal voltages to a telephone line under the control of a microcomputer within the telephone exchange comprises four charge pumps, each comprising a...
4549045 Method to operate through a telephone line one automatic phone answering equipment specified among a plurality, and apparatus to carry it out  
A method and apparatus are provided to control a subscriber's phone system including, at least, one automatic telephone answering equipment. When a calling party dials the phone number of a...
4540854 Subscriber line interface circuit  
A transformerless, fully balanced, telephone line circuit is provided. Two differential amplifiers are employed, one for incoming signals and the other for outgoing signals. The latter drives the...
4540855 Detecting signals within a passband on a telephone line  
An improved combination of a hardware and digital signal processing filter for detecting pick-up of a telephone call, solely through audio information on the telephone line. The apparatus employs a...
4539438 Active impedance transformer assisted line feed circuit with supervision filtering  
A supervision filtering function is included in a line circuit wherein tip and ring voltage amplifiers supply energizing current to a two wire communication line via tip and ring primary windings...
4535201 Ground start detection in telephone loop signalling circuit  
A circuit configuration for a telephone loop signalling circuit, for detecting a ground start condition on a telephone line. The circuit operates without modification under both loop start and...
4525603 Ring and line monitor for answering machine  
A circuit and system is provided in a telephone answering system and which responds to direct current voltage differentials on the telephone line, independent of the actual direct current voltage...
4524244 Digital and voice telecommunication apparatus  
The present invention relates to a communication apparatus for transmitting and receiving analog voice and digital data signals to and from a telephone line or telephone lines to one or more users,...
4524246 SLIC II--common-mode current rejection  
A subscriber line interface circuit using auxiliary current detectors in the legs of a bridge whose input is the subscriber load and a control circuit connected to the auxiliary detectors for...
4506112 Telephone set including a circuit for seizing the line without lifting the handset off the gravity switch  
Telephone sets associated with terminal units such as modems or telecopiers generally need to be used without the handset being lifted off the gravity switch. Such telephone sets also tend to...
4495494 Detector circuit for communication lines  
A detector circuit detects one of two impedances presented by a communication line for each one of a plurality of operative modes. The circuit comprises a network having three parallel branches....
4489221 Telephone line/subscriber equipment disconnect apparatus  
A disconnect signal (e.g. 130 volts D.C.) is applied at the telephone central office to the tip and/or ring lines. A latching relay adjacent to the subscriber equipment operates directly responsive...
4484028 Digital loop transceiver having a power up/down circuit  
In a digital telephone system, a digital private automatic branch exchange (PABX) has a plurality of digital line cards for coupling the PABX to respective digital subscriber sets via subscriber...
4477698 Apparatus for detecting pick-up at a remote telephone set  
An improved combination of a hardware and digital signal processing filter for detecting pick-up of a telephone call, solely through audio information on the telephone line, is disclosed. The...
4456791 Off-hook detector with reduced sensitivity to common mode  
An off-hook detector for use in subscriber line interface circuits to indicate status of the subscriber line, or loop, exhibits reduced sensitivity to common mode or longitudinal currents. A...
4455456 Digital supervisory circuit for a telephone system  
The digital supervisory circuit comprises an amplitude comparator and EXCLUSIVE-OR gate to provide an output signal indicating the difference in time an input signal is above and below a...
4435622 Latching relay hold circuit for a telephone instrument  
In a hold circuit connectable to a subscriber telephone line, a line voltage storage capacitor is momentarily connected to the subscriber line charging to line potential and providing trigger...
4433213 Subscriber's line circuit for telecommunications networks  
A subscriber's line loop including a terminal station and symmetrically arranged in the loop relative to the station two constant current sources. Each current sources has a power unit defining an...
4429185 Voltage detector circuit  
A voltage detector circuit for detecting a DC voltage on a line in the presence of a substantially fixed frequency AC voltage. The circuit may be used to detect call originations on a telephone...
4419542 Battery feed circuit  
The battery feed circuit of the present invention does not rely principally on balanced current generation circuitry but, instead, uses a feedback circuit to ensure the production of the required...
4410765 Telephone call routing and charging system  
A telephone call routing and charging system using processor circuitry can automatically select the most economical route for individual telephone calls. The system includes a signal direction...
4410766 Power saving line circuit  
This invention is a circuit for reducing the power requirements for a subscriber's line where the loop length is short. The circuit senses the line current in the off-hook condition, and if the...
4402039 Telephone line circuit  
A floating, constant power, battery feed circuit wherein a single transformer is used to perform the functions of battery feed and audio coupling. AC feedback is used to control the dynamic output...
4392023 Off-hook telephone sensing system  
An off hook telephone sensing system for use with a voice and data transmission system, including a transaction terminal coupled to a telephone line for data transmission, a telephone instrument...
4345115 Telephone line interface  
A telephone subscriber's line interface for a system in which the telephone instrument and the connections therefrom to the exchange use analogue, while the exchange is digital is described, in...
4326104 Current detector  
According to the present invention there is provided a current detector useful in interconnection of an automatic telephone exchange with a central office via TIP and RING leads and comprising;...
4322586 Transformerless line interface circuit  
A line circuit includes a fixed resistance feed consisting of a pair of resistors connected in series with a d.c. power source and tip and ring leads of a communication line. A variable current...
4317963 Subscriber line interface circuit utilizing impedance synthesizer and shared voltage source for loop current regulation control  
A subscriber line interface circuit is described wherein current supplied to a telephone subscriber line from a shared voltage source such as a DC/DC converter is regulated thereby permitting a...
4317964 Off-hook/on-hook status check circuit  
An off-hook/on-hook status check circuit is adapted to be connected in series with either the tip (2) or the ring lead (3) of a telephone subscriber loop (1) at a location remote or apart from the...
4315106 Apparatus for regulating current supplied to a telephone line signal of the type employed in digital telephone systems  
Circuit apparatus for supplying a regulated loop current to a two conductor loop telephone line includes first and second line feed resistances, each having one terminal connected to a respective...
4314106 Line circuit  
A line circuit comprising a terminal for connection of a wire of a subscriber's line for applying thereto a line current which is determined by the impedance of the subscriber's line and an...
4313034 Connecting circuit for a telephone line  
Connecting circuit for a telephone line comprising a pair of amplifiers whose outputs are connected to the one and to the other wire of the telephone line, respectively. Longitudinal currents which...
4306122 Telephone line circuit  
The line circuit comprises at least a driver stage 1 having an amplifier. This amplifier is provided with a feedback circuit for forming a virtual output impedance which functions as a supply...
4304970 Telephone status monitor apparatus  
A telephone status monitor apparatus for determining the on/hook and off/hook conditions of a telephone connected across tip and ring terminals across which a ringing voltage may be present and...
4297531 Circuit for suppressing noise influences in the evaluation of signal states on transmission lines  
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...
4291199 Communication system tracking arrangement  
A communication system call tracking arrangement is disclosed which allows a telephone station user to selectively determine the busy-idle status of any other telephone station served by the same...
4282407 Telephone loop resistance detector  
The disclosure shows a telephone range extender which is automatically adaptable to the length of the connected subscriber loop. A loop resistance detector within the range extender discriminates...
4277648 Telephone monitoring apparatus  
Each telephone line of a telephone network is individually monitored to determine its on/off hook status and any control pulses or tones being impressed thereon. Each monitor unit when it has...
4270027 Telephone subscriber line unit with sigma-delta digital to analog converter  
A digital to analog converter is employed in the digital line circuit of a telephone system and operates to convert a digital signal indicative of an analog speech signal back into a replica of the...
4221936 Loop to ground start circuit  
A circuit for translating a loop start to a ground start signal in a communication system interconnected via a tip lead and a ring lead, in which the ring lead is connected to a source of potential...
4211896 Subscriber's circuit with a symmetrical amplifier  
Subscriber's circuit for connecting a subscriber's line to a telephone exchange, comprising a symmetrical amplifier which is arranged between two feed points having different potentials, the...
4178486 Ring sensing circuit for use with a service evaluation system  
A ring sensing circuit for use in conjunction with a line connected between a subscriber and a switching center. The subscriber line is monitored by a service evaluation system. The ring sensing...
4156799 Automatic disconnect circuit  
An automatic disconnect circuit is described for disconnecting a remote telephone in resonse to a hang-up click generated when the remote telephone goes on-hook. To distinguish a remote hang-up...
4144408 Telephone ringing extender  
A telephone ringing extender is shown which includes a ringing signal detector and a switch. In response to ringing signals, the ringing extender grounds the tip conductor to operate telephone...
4132864 Digital measurement of the DC value in an AC signal adapted to telephone off-hook detection  
The duty cycle of an AC telephone off-hook signal is measured by means of comparing it with the duty cycle of a known AC signal having a duty cycle of 0.5 because it has a DC component of zero....
4124781 Telephone toll restrictor  
An improved telephone toll restrictor utilizing both current and voltage sensors having substantially infinite input impedance during the on-hook condition. A timing circuit is provided to restrict...
4118603 DC signaling circuit for use in conjunction with isolation transformers  
The present invention relates to a DC signaling circuit operatively associated with a communication system having an isolation transformer interconnected between a central communication exchange...
4086439 Class of line identifier apparatus and method therefor  
An apparatus identifying a class of called telephone lines by extending an identity signal back over the called line to a calling central operator or control. The identifier apparatus includes a...
Matches 301 - 350 out of 396 < 1 2 3 4 5 6 7 8 >