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Scientific American ; Jan. 2 edition, 1909
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| Number | Title | Issue Date |
| 7907720 | Test method for line equipment including a hybrid circuit and line equipment for its implementation The invention relates to methods for testing analog telephone line equipment including, in particular to detect faults in their hybrid resistor arrays. It consists in isolating the equipment from the telephone line and then applying the normal ringing signal ... | 03/15/2011 |
| 7190769 | Apparatus for controlling operation of a recording device with a telephone instrument An apparatus for controlling operation of a recording device with a telephone configured for orientation in a first state and a second state includes: (a) an information conveying section for conveying information from the telephone to a recording locus in the recor... | 03/13/2007 |
| 5867560 | Remote hang-up detector A communications detector for detecting remote user hang-up or disconnection by a telephone answering machine (TAM). The remote hang-up detector (RHUD) may operate in conjunction with a modem and does not affect transmission and receipt of modem signals a... | 02/02/1999 |
| 5764755 | Ring-signal generation in a SLIC A ring generator circuit is included in a subscriber line interface circuit (SLIC) for providing a high voltage ring signal to a plurality of ringers at the same time. The ring generator circuit includes an adder and divider circuit connected to receive a... | 06/09/1998 |
| 5745563 | Telephone subscriber line circuit, components and methods A subscriber line circuit for a telephone network having current controlled switches and current sources. Methods of making and using the components are also disclosed.... | 04/28/1998 |
| 5636274 | Switch controller and method A circuit and method for reducing power consumption during operation of a solid state switch that controls connection of a source of alternating current to a load includes a circuit for determining a voltage across the switch. The switch is operated upon ... | 06/03/1997 |
| 5583934 | DC level control for an electronic telephone line card DC level control for an electronic telephone line card which filters the DC component from the input audio signal, determines the gain setting of the transmit path, develops a DC adjust voltage opposite to that of the DC shift component and subtracts the ... | 12/10/1996 |
| 5577114 | Subscriber line control apparatus to concurrently detect change in line state for subscriber lines and determine validity of timer device A subscriber line control device utilizes a scan input table and a last look table. The scan input table stores respective current line states of a plurality of analog subscriber lines. The last look table stores respective preceding line states of the pl... | 11/19/1996 |
| 5568547 | Subscriber circuit provided with a circuit for monitoring a subscriber instrument A subscriber circuit comprising a monitor circuit operating with a power supply voltage supplied to a subscriber instrument and monitoring an operation of the subscriber instrument for generating a monitor signal indicative of the result of monitor, and a... | 10/22/1996 |
| 5539820 | Protection of active telephone line interface circuits A telephone line interface circuit with d.c. amplifiers coupled to tip and ring paths is protected against transient voltages by a crowbar-type protection device coupled via a diode bridge to the tip and ring paths, positive and negative terminals of the ... | 07/23/1996 |
| 5506891 | Method and apparatus for detecting the connection status of an extension phone connected to a voice/fax/data modem A detector circuit is provided for detecting the off-hook status of the extension telephone line. The detector is connected to tip and ring lines of the telephone line for determining a change in the voltage between the tip and ring lines. The detector in... | 04/09/1996 |
| 5450485 | Detecting whether a telephone line has been disconnected Apparatus for detecting whether a telephone call has been disconnected, which apparatus includes: (a) a click detector for detecting a click and for generating a "click indication"; (b) a telephone handset impact detector for detecting a telephone handset... | 09/12/1995 |
| 5259022 | Detector for use with an automatic disconnect feature in a telephone answering machine In a telephone answering machine, a detector for a automatic disconnect function uses a first amplifier to detect, amplify, and invert small input signal changes, and second amplifier to detect large input signal changes and a logic arrangement responsive... | 11/02/1993 |
| 5172409 | Precision FET control loop A telephone line card circuit includes an operational amplifier circuit having first and second inputs and an output. A field-effect transistor circuit has first, second and control electrodes, the control electrode is coupled to the output of the operati... | 12/15/1992 |
| 5163087 | Delivery of customer data base key using automatic number identification An enhanced "800" service translates an Automatic Number Identification (ANI) of a calling party into a customer data base key defined by the called party. The customer data base key is then provided by the enhanced "800" service to the called party in pl... | 11/10/1992 |
| 5019730 | Information separation device An information separation device having a transformer operating as a separating filter to separate transmitted direct current power and alternating voltage information. The transformer has at least two windings on a first side holding power in reserve. Be... | 05/28/1991 |
| 4958371 | Method and apparatus for determining when a telephone handset is off-hook Apparatus in an automatic telecommunications system which communicates between a central location and at least one remote location over the switched telephone network, senses changes in loading of the telephone line which correspond to a telephone going o... | 09/18/1990 |
| 4935959 | Two-wire telecommunications line detection arrangements A loop closure detector for a two-wire telephone line comprises a four-arm resistive bridge, in which the four arms are constituted respectively by a first battery feed resistor, the two-wire line in series with a second battery feed resistor, and two res... | 06/19/1990 |
| 4897871 | Apparatus for transmitting and/or receiving balanced signals on a two-wire telecommunication line A transformerless hybrid circuit arrangement for a subscriber line interface circuit of a telecommunications exchange is disclosed. A preferred embodiment of the hybrid arrangement comprises a first and a second operational amplifier plus a differential a... | 01/30/1990 |
| 4827505 | Subscriber line interface circuit A subscriber line interface circuit receives and twice inverts currents from a 2-wire subscriber line and returns the currents to the subscriber line so longitudinal input impedance is low. Any differential input current in the subscriber lines is bypasse... | 05/02/1989 |
| 4760595 | Subscriber line interface circuit having means for combining DC and AC feedback signals A subscriber line interface circuit comprises a balanced amplifier having positive and negative inputs for amplifying a voltage thereacross to generate a pair of mutually complementary voltages across true and complementary outputs. Four resistors of a fi... | 07/26/1988 |
| 4742538 | Current source and off-hook detector The invention relates to circuitry for providing and monitoring the status of telephones, especially those used in conjunction with advanced telephone answering machines, such as is also disclosed herein. The voltage on the extension line leading to the t... | 05/03/1988 |
| 4734935 | Communication system with remotely controllable signal receiving means A communication system having remotely controllable signal receiving means for automatically setting the receive function for a start-signal transmitted from a terminal device and for changing the receive function when the terminal device is changed. At s... | 03/29/1988 |
| 4677664 | Method and apparatus for an improved ring trip detection telephone circuit A telephone circuit for ring trip detection that can be monolithically integrated, includes a current transducer coupled to a user's telephone line, and an integrator circuit. The output current of the current transducer is proportional to the line curren... | 06/30/1987 |
| 4648109 | Light emitting diode message waiting lamp circuit A circuit providing a message waiting indication using a light emitting diode and a constant current surge protected circuit for use with PABX extension telephone instruments. Recently developed light emitting diodes operated with current of one milliampe... | 03/03/1987 |
| 4599494 | Ring sense telephone tone ringer circuit A sense circuit which senses when the magnitude of a full wave rectified current exceeds a predetermined threshold value comprises current mirrors for diverting a very small portion of the current to an output wherein this current is filtered to produce a... | 07/08/1986 |
| 4555593 | Electronic telephone relay An electronic relay circuit for replacement of an A-type relay in a step-by-step selector and connector of a telephone exchange system is implemented with a first operational amplifier (10) connected to the tip (T) and ring (R) conductors of a telephone l... | 11/26/1985 |
| 4514595 | Active impedance line feed circuit A line circuit includes tip and ring voltage amplifiers each having an output resistively connected via tip and ring feed resistors to tip and ring leads in a telephone line. The tip and ring feed resistors have closely matched ohmic values, and are part ... | 04/30/1985 |
| 4451703 | All electronic interface for telephony system A line circuit for connecting a subscriber line to a telephony system that avoids the use of electro-mechanical elements such as relays. A bridge circuit includes a bilateral current gate in each of the tip and ring lines that can couple or inhibit signal... | 05/29/1984 |
| 4446338 | Telephone lines status sensor A lines status sensor provides for monitoring of the operating status of one or more telephone lines at an associated telephone station apparatus. The lines status sensor includes a translation circuit being responsive to potential differences appearing a... | 05/01/1984 |
| 4431871 | Solid state relay A solid state relay provides for a discontinuous transfer contact function. The solid state relay includes a first field effect transistor (FET) in a first switch, and second and third FETs in a second switch. The first and second FETs are each connected ... | 02/14/1984 |
| 4360709 | Loop detecting circuit A circuit for detecting a closed loop formed by actuation of a telephone set, the loop being indicative of a connection between the telephone set and an exchange through a ring line and a tip line. The detecting circuit comprises generators for generating... | 11/23/1982 |
| 4337378 | On-hook/off-hook detector circuit An on-hook/off-hook detector circuit (10) is included within a telecommunications integrated circuit. A tone generator power signal (VG) is monitored as a status signal to determine when a telephone switch hook is in either an on-hook or off-ho... | 06/29/1982 |
| 4319091 | Dial pulse restorer A dial pulse restorer for receiving and restoring telephone dial pulses which may be distorted, and also for discriminating telephone-hang-up pulses which may be applied to a telephone line when a remote telephone coupled to the telephone line hangs up. A... | 03/09/1982 |
| 4310724 | Current detector circuit A current detector circuit, preferably for use in telephone equipment, to detect the on-hook and off-hook conditions of of such equipment, includes two equal transformers which have primary coils mounted in series and secondary coils mounted in series opp... | 01/12/1982 |
| 4297532 | Interfacing circuit status detection arrangement in a telephone exchange There is provided a telephone exchange including a switching network, a plurality of interface circuits whose corresponding transmit/receive paths are connected to the switching network, a data generator connected to the interface circuits to sequentially... | 10/27/1981 |
| 4158109 | Interference insensitive line supervision circuit Interference insensitive line supervision circuit for subscriber's line having a given working range for the line potentials. A call can be simulated by the occurrence of overvoltages. Means are applied which supervise the occurrence of overvoltages. In t... | 06/12/1979 |
| 4115664 | Discriminating network for telephone switching signals A network discriminating among switching signals appearing on a pair of talking wires of a telephone line comprises a light-emitting diode in series with each wire and a phototransistor illuminable thereby. The phototransistors energize respective amplifi... | 09/19/1978 |
| 4079208 | Telecommunications transmission and signalling circuits A d.c. signal detector circuit for a telephone exchange which comprises a level detector which is so connected that it can sense current flowing in a telephone line. The level detector is arranged to switch states when a loop is established in a telephone... | 03/14/1978 |
| 4064377 | Electronic hybrid and hybrid repeater An electronic hybrid for coupling signals between two wire and four wire transmission circuits, and capable of meeting the operating requirements of practical telephone systems. The hybrid includes a pair of terminating impedances serially connected betwe... | 12/20/1977 |
