Abstract: A method and apparatus is provided for DC feed control for a line card. The method includes determining if the line card is operating in a current limit region of a DC feed curve and synthesizing a curve in the current limit region. The method further includes determining a loop voltage based on the synthesized curve, and applying the loop voltage to the subscriber line. The apparatus includes logic capable of determining if the line card is operating in a current limit region of a DC feed curve and capable of determining a loop voltage based on a synthesized curve in the current limit region. The apparatus further includes circuitry for applying the loop voltage to the subscriber line.

Abstract: In a telephone power source circuit, a direct current from a network is used to charge an input capacitor via an input current limiting resistor. A resultantly charged voltage is inputted to and is converted by a DC/DC converter to produce an output voltage. In parallel with the input current limiting resistor, a limit removing unit including a switching transistor is arranged. The output voltage is delayed by a delay circuit to activate a driving transistor, which drives the switching transistor. The input voltage to the converter is monitored by an input voltage sensor. Therefore, the telephone power source circuit copes with a plurality of hubs of different power supplying specifications in an internet (IP) telephone network in which telephones are connected to a local-area network of the IEEE802.3 standard and the like.

Abstract: A method and apparatus are provided for maintaining communication across an isolation barrier even if the external circuitry to which it is connected enters a low-power mode. In normal operation the isolation barrier local clock is synchronized with a clock signal provided by the external circuitry. If the external circuitry enters a low-power mode, its clock signal often slows or stops. In that case, the local clock in the isolation barrier switches to a free-running mode, wherein a VCO voltage input is provided by a bias voltage generator instead of by a PLL circuit. The VCO thus continues to provide a local clock signal in order to allow communication of information across the isolation barrier even if the external circuitry is not active. This enables the isolation barrier to receive and process an external signal, such as a ring signal, in low-power mode.

Abstract: A system within a PC server cabinet for receiving an externally supplied loop feed voltage (−48 VDC) and generating a ringing voltage (75 VAC) from the loop feed voltage. For universal applicability, the ringing voltage generator is preferably located in a 5.25 inch standard disk-drive housing of the cabinet, allowing it to fit into any PC. All required telecommunications signaling and power is thereby provided in the PC while limiting accidental user exposure to hazardous ringing signal voltage levels.

Abstract: A telephone line driven power supply and power supply method capable of creating high yield, low voltage power using power drawn from a telephone line and supplementing the low voltage power with power from a battery-powered host device, such as a laptop PC, when the voltage level falls below a predetermined voltage level. The telephone line power supply includes a polarity guard, a gyrator, an oscillator, a pulse circuit, an inductor, a startup circuit, a converter, a shunt regulator, and a combiner circuit. The method includes supplying line power from power drawn from a telephone line, receiving host power from a host device, supplying the line power to an electrical device, and supplementing the line power with the host power when the voltage level of the line power falls below a predetermined level.

Abstract: An apparatus. and method of powering a cable telephony service platform (CTSP) in a hybrid fiber coax (HFC) network are provided which utilizes a combination of power from a local AC driven power source having a back-up battery for powering the CTSP within a network interface unit (NIU) during interruptions in normal AC power, and a network generated charging current which maintains the battery at full float voltage charge irrespective of the duration of any such interruptions in AC power delivery. Thus, the present invention minimizes power required to be delivered by the network while still ensuring support of reliable lifeline telephony service for cable telephony on an HFC network.

Abstract: An isolation system is provided that is suitable for use in telephony, medical instrumentation, industrial process control and other applications. Preferred embodiments of the invention comprise a capacitive isolation barrier across which a digital signal is communicated. The system provides a means of communication across the isolation barrier that is highly immune to amplitude and phase noise interference. Clock recovery circuitry may be employed on one side of the isolation barrier to extract timing information from the digital signal communicated across the barrier, and to filter the effects of phase noise introduced at the barrier. Delta-sigma converters may be disposed on both sides of the isolation barrier to convert signals between analog and digital domains. An isolated power supply may also be provided on the isolated side of the barrier, whereby direct current is generated in response to the digital data received across the isolation barrier.

Abstract: Control circuit and method for regulating the supply voltage of an SLIC circuit (15), having a monitoring circuit (36) for calculating an SLIC supply voltage which is required to reach a nominal supply current (Inom) for an analogue terminal (2) which is connected to the SLIC circuit (15); and having a DC/DC converter (53), which is controlled by the monitoring circuit (36), for converting a battery voltage (Vbatt) to the calculated SLIC supply voltage.

Abstract: A power management circuit for use in a terminal interface device such as a modem which converts available power from a terminal or host device such as a computer into usable standby power for use when the terminal interface device is non-operational. The power management circuit is additionally comprised of a voltage regulator which, when a terminal interface device becomes operational, is enabled and regulates available voltage and current into usable power as available from the interfacing communication network. The preferred embodiment of the power management circuit is further comprised of a programmable hold current generator which enables a terminal interface device incorporating the power management circuit to be compatible with multiple communication networks having diverse hold current specifications. The use of power available from the communication network in generating the operational voltage greatly reduces interference injected onto the communication network.

Abstract: A signal line driving circuit with power control for selectively reducing internal power dissipation when driving an external load. While driving the external load with a constant current the output voltage generated across such load is monitored. If the load impedance decreases sufficiently to cause the output voltage to fall below a predetermined threshold value and, therefore, cause the voltage across the signal line driving circuit to increase, the magnitude of the power supply voltage is automatically reduced, thereby reducing the voltage across the signal line driving circuit. Such a signal line driving circuit is particularly advantageous as a subscriber line interface circuit (SLIC). As the subscriber goes from an on-hook condition to an off-hook condition and if the subscriber loop is sufficiently short (or low in impedance), a lower power supply voltage is used to minimize the power dissipation of the SLIC while still maintaining the required subscriber loop current.

Abstract: A power supply has a plurality of single line interface circuits (20, 22, 24 and 26) each connected by a respective line, to a respective telephone (4, 6, 8 and 10) or other telecommunications device. Each SLIC applies a sufficient voltage derived from a battery to the line to operate the respective telephone, and dissipate any excess power supplied by the battery. The apparatus includes common power regulation means (30), which incorporates a switch mode power supply unit (68), and which monitors the voltages being supplied by the SLICs at any one time and reduces the voltages applied to the SLICs to substantially the maximum voltage required by any one of the SLICs, thereby reducing the amount of power dissipated by the SLICs.

Abstract: A CMOS implementation for a DC holding circuit in direct access arrangement (DAA) circuitry is disclosed that provides desirable inductive behavior while minimizing power dissipation required by the CMOS integrated circuit, particularly at high loop currents. The DC holding circuitry disclosed may include MOS transistors located on a CMOS integrated circuit and an off-chip power dissipating resistor that acts to dissipate power external to the CMOS integrated circuit. The CMOS implementation disclosed also allows a path for drawing DC current to power other CMOS circuits (e.g. ADCs and DACs) in the CMOS integrated circuit.

Abstract: In one embodiment, the present invention is directed to a system and method for power-feeding a line coupled to an exchange without disturbing the operation of the exchange. The system may include a power-feeding unit coupled to the line and an adapter coupled to the line, the adapter also coupled to or embedded in a current-consuming device coupled to the line.

Abstract: A system and method is provided for supplying power over a home phone line network in a manner that is interoperable with other voice and data services operating on the same network. The system includes a power source coupled to the home phone line network. The power source includes an AC signal generator that generates an AC signal at a selected frequency. The power source also includes a band pass filter for removing unwanted harmonics from the AC signal, thereby generating a filtered AC signal for powering one or more devices on the home phone line network. One or more devices attached to the home phone line network, such as a telephone adapter or telephone, receives the filtered AC signal. Each device comprises a second band pass filter and an AC/DC converter. The second band pass filter passes the filtered AC signal to the AC/DC converter and prevents the introduction of undesired harmonics onto the home phone line network from the AC/DC converter.

Abstract: Known is a wire bound telecommunications device to be coupled to telecommunication lines comprising a transmission circuit coupled between the telecommunications lines, which transmission circuit comprises a power supply circuit for forming a supply voltage from a telecommunications line voltage, whereby the power supply circuit comprises sensing means for sensing a telecommunications line current and adjustment means for adjusting the supply voltage, a supply voltage terminal being coupled to the sensing means. In the known device, no optimal matching is obtained for the load line of the power supply to a DC-mask for line voltages as a function of a line current as prescribed for a given country. A more optimal matching is proposed.

Abstract: A CMOS implementation for a DC holding circuit in direct access arrangement (DAA) circuitry is disclosed that provides desirable inductive behavior while minimizing power dissipation required by the CMOS integrated circuit, particularly at high loop currents. The DC holding circuitry disclosed may include MOS transistors located on a CMOS integrated circuit and an off-chip power dissipating resistor that acts to dissipate power external to the CMOS integrated circuit. The CMOS implementation disclosed also allows a path for drawing DC current to power other CMOS circuits (e.g. ADCs and DACs) in the CMOS integrated circuit.

Abstract: A fixed subscriber unit includes a voltage measuring unit which acquires a DC input voltage value to be applied to a power circuit, and a comparator/judging unit which compares a preset DC voltage with the DC voltage measurement and judges whether the power circuit is driven by the DC voltage from an AC/DC adaptor or by the DC voltage supplied from a charge battery. When the power circuit is driven by the charge battery, the available operation time of the fixed subscriber unit is calculated by a calculation unit from the DC voltage measurement. The information thus obtained on the driving power state and/or the available operation time are aurally or visually notified to the user by a notification unit. The user thus can select an appropriate method of using the fixed subscriber unit according to the prevailing situation.

Abstract: An automatic power supplying device for providing power for a CPU of a telephone to activate the CPU and wake up a downstream circuit including for example a speech processor, a voice amplifier, etc., is disclosed. The automatic power supplying device includes a recharging circuit providing the power for the CPU for a predetermined period when there is a coining phone call and the telephone is hooked off. After the predetermined period, the CPU is supplied thereto power which is transmitted along the telephone line and accompanies the phone call signal. The CPU of the telephone is activated only when the telephone is in a hook-off state according to the present invention so that the life span of the CPU can be extended, compared to the conventional telephone.

Abstract: A dual-supply line-interface circuit (100) uses a −48V power supply (VBAT1) to drive long subscriber loops (120) and uses a −28V power supply (VBAT2) to drive short subscriber loops. For intermediate-length loops, a dual-slope current-feed profile (FIG. 4) is employed to limit the line-circuit's power dissipation. The line-interface circuit operates in an apparent constant-current mode, generating about 40 mA of differential line current using the low power supply, up to a threshold line voltage of about 25V, which is equal to the low power supply voltage minus required overhead. For longer loops, the line-interface circuit switches to a second constant-current mode, generating about 22 mA of differential current using the high power supply, which maintains the loop current constant until it drops to the 48V resistive-feed value.

Abstract: An Ethernet device power transmission system includes an input transformer, an output transformer and a pair of twisted pair conductors. The input transformer includes a pair of primaries for connection to a source of Ethernet data. The input transformer also includes a pair of secondaries, each having a center-tap. A first twisted pair conductor is connected across the first secondary, a second twisted pair conductor is connected across the second secondary and a DC-bias is provided between the respective center taps of the first and second secondaries. At the local end, the output transformer includes a first and second center-tapped primary and a first and second secondary for connection to the load device. The first and second primary center taps are connected to a power processor for extraction of DC power.

Abstract: An apparatus and method for subscriber loop powered calling identity delivery on call waiting apparatus provides battery only operation or extended battery life in a calling identity apparatus intended for off-hook and on-hook operation. The apparatus and method of using comprises a caller identification data receiver coupled to the subscriber loop for decoding caller identification tones and a CAS tone detector for detecting an alerting signal having at least one tone detector power supply input. Further comprised is a power supply circuit wherein the power supply's input is coupled to the subscriber loop for supplying power from the subscriber loop to the CAS tone detector.

Abstract: An adapter circuit PSA includes a comparator module OA, and a regulation module RM for normally adjusting the value of an output voltage Vout intended to be applied to an external circuit to a predetermined nominal regulation value Vreg0. In response to a measuring module SC sensing a reverse current flow at the output which is produced when an external power supply source in the external circuit connected to the output of the adapter circuit PSA includes an effective voltage source Vext which imposes on the output a voltage VDD which has a higher value than the nominal regulation value Vreg0, feedback coupled to an input to the comparator module OA is activated to raise the value to which the output voltage VDD is regulated to equality with the value of the effective voltage source Vext, thereby nulling the output current.

Abstract: A line-powered circuit for connecting a telephone line to a telephone voice circuit comprised of a digital part and an analog part. The digital part is a logic circuit for generating a line connect signal that indicates a telephone line should be connected to the voice circuit. The power for operating the logic circuit is provided by the line voltage associated with the tip and ring leads of the telephone line. The analog part comprises a first switch means for connecting the voice circuit to the tip lead in response to the line connect signal, and a second switch means for connecting the voice circuit to a ring lead in response to the line connect signal.

Abstract: A power feeding system includes a line state detector for detecting an operation state of each of a pair of 2-wire subscriber lines connected to the exchange equipment and a transformer for supplying the DC power to the subscriber terminal through each of the pair of 2-wire subscriber lines connected to the subscriber terminal. When the detector detects a subscriber line test state, a switch circuit detaches the transformer from each of the pair of 2-wire subscriber lines and directly connecting the exchange equipment to the subscriber terminal through each of the pair of 2-wire subscriber lines.

Abstract: This invention relates to a portable terminal equipment using a battery as a power source. The equipment determines whether or not battery voltage VB is lower than a voltage value V1 in a standby state or a speaking state (ST1 and ST8). The voltage value V1 is set to such a value that the equipment is capable of generating an outgoing call and making a speech during a set period of time, when the battery voltage VB is equal to the value V1. When VB<V1, the equipment shifts to a low-consumption standby mode in which a small amount of current is consumed (ST14). When the equipment is set to a speaking state, it generates a warning by means of alerting voice and so on to warn the user that the telephone communication will be broken after a expiration of a set period of time (ST10) .

Abstract: A subscriber loop interface circuit is provided that includes a current directing element for directing current from the output stage of line interface amplifiers. The current is directed to a secondary power supply having a magnitude lower than the conventional primary power supply of a subscriber loop interface circuit in supplying power to a subscriber loop.

Abstract: A CMOS implementation for a DC holding circuit in direct access arrangement (DAA) circuitry is disclosed that provides desirable inductive behavior while minimizing power dissipation required by the CMOS integrated circuit, particularly at high loop currents. The DC holding circuitry disclosed may include MOS transistors located on a CMOS integrated circuit and an off-chip power dissipating resistor that acts to dissipate power external to the CMOS integrated circuit. The CMOS implementation disclosed also allows a path for drawing DC current to power other CMOS circuits (e.g., ADCs and DACs) in the CMOS integrated circuit.

Abstract: A network interface device includes a base, a cover and a circuit board secured in the base. The circuit board includes terminations for input and output communication lines. Each pair of input and output communication lines corresponds to a single standard telephone line, a high speed data line or other type of line. The communication line terminations may be implemented as insulation displacement connectors, and the cover may include projections on its inner surface such that closing the cover also closes the insulation displacement connectors on the circuit board. For each communication line, the circuit board may include a subscriber bridge which establishes a breakable connection between the input and output line terminations via traces in the circuit board. In fixed wireless, fiber-to-the-home (FTTH) and other similar applications, the circuit board may also include terminations for input and output power lines, and the base and cover may be extended to accommodate an uninterruptible power supply.

Abstract: An improved line interface device and an improved xDSL modem for use in connecting data communications equipment to a xDSL line is disclosed. The line interface device provides the required isolation between the xDSL line and the communications equipment using optical isolation or capacitive techniques, as well as provides the power necessary to produce the transmit signal levels required by the communications services by utilizing a switching power supply deriving its power from a source isolated from the line, and including a transformer for isolating the source from the xDSL line. By switching at high frequencies the size of the transformer can be sufficiently small so that the interface device and supply can be provided in accordance with small form factor requirements.

Abstract: A line card integrates subscriber line interface circuitry, A/D and D/A converters, and digital signal processing technology. The digital signal processing technology performs many line card tasks such as switch hook detection, ground key detection, DC feed control, polarity reversal, ringing tests, fault detection, power cross detection, and ring trip detection. A line card having a digital signal processor supports both integral and external ringing signal generators. During application of a ringing signal, the line card detects ring trip conditions while discriminating against short duration short circuits. The line card includes programmable features that facilitate adaptation to varying regional ring trip detection and short duration short circuit discrimination specifications and subscriber loop characteristics.

Abstract: A power supply circuit includes a line voltage forming circuit and a supply voltage forming circuit. The line voltage forming circuit forms a voltage that is proportional to a line voltage provided by a telecommunication line, and the supply voltage forming circuit forms a second voltage from the first voltage. A sensing circuit senses the telecommunication line and provides a sensor signal that is representative of the power provided by the telecommunication line. The line voltage forming circuit is controlled by the sensor signal such that the slope of a load line characteristic of the line voltage forming circuit is modified when the sensor signal is above a predetermined threshold signal. The load line characteristic defines an increase of the line voltage with an increase of the line current provided by the telecommunication line.

Abstract: The modem of a portable computer device draws a portion of its required power from the telephone line using a low noise switching power supply. The switching power supply can alternatively or additionally assist in keeping the battery of the portable computer device charged. The generation or propagation of electrical noise on the input telephone line is minimized by actively maintaining a constant input impedance from the telephone line to the modem. In one embodiment, a switchable shunt impedance is placed in parallel with the input to a PWM switching power supply and actively controlled to maintain the impedance of the input of the PWM switching power supply constant to the extent that a constant current draw is maintained.

Abstract: A battery powered computer system includes an add-on device, such as a modem, with a power supply that uses power from a telephone line to provide power to the modem. In one embodiment the power supply is an adaptive power supply that uses power from both the telephone line and the battery of the computer system. The adaptive power supply determines the maximum power available from the telephone line and delivers that power to the modem. If the power from the telephone line is not sufficient for the modem, the adaptive power supply supplements the power with the power from the computer system. In one embodiment, the adaptive power supply uses power time division multiplexing to share the power from the telephone line and the computer system.

Abstract: A method and apparatus to receive and demodulate call related information, e.g., Caller ID information, in an audio codec placed on the line side and powered by current drawn from the telephone line. The audio codec includes a 1st order &Sgr;/&Dgr; A/D converter to digitize the signal from the telephone line with &Sgr;/&Dgr; modulation. The 1st order &Sgr;/&Dgr; A/D converter may be a scaleable component capable of alternative operation in a 2nd order. The &Sgr;/&Dgr; encoded digitized signal is digitally processed by a DSP including an amplifier module, a digital filter, a limit/slice module, and an FSK decoder to receive and output the call related information. Placement of the audio codec on the line side and the scaleable &Sgr;/&Dgr; A/D converter provides significantly reduced power requirements for the audio codec, thus allowing operation from power derived from the telephone line.

Abstract: A digital direct access arrangement (DAA) circuitry may be used to terminate the telephone connections at the user's end that provides a communication path for signals to and from the phone lines. Briefly described, the DAA provides a programmable means for the DC termination for a variety of international phone standards. The invention may also be utilized with means for transmitting and receiving a signal across a capacitive isolation barrier. More particularly, a DC holding circuit is provided that has switchable time constants. A first time constant may be utilized during a first operation phase immediately after off-hook conditions to allow for fast settling times. Then, a second operation phase is entered in which a second time constant may be utilized. During the second operation phase the DC holding circuit operates slower to create improved low frequency performance.

Abstract: The portable remote terminal apparatus comprises a CPU, a clock oscillating means and a keyboard for operation, and is arranged to execute communication in a time sharing system.

Abstract: Remote supply circuitry for remotely supplying a subscriber connections in a communications system wherein subscribers can be connected to a central point via subscriber lines. Subscriber supply voltage or power supply is provided for each subscriber via a supply voltage source assigned to the subscriber and at least one supply isolating element wich is connected in series with the subscriber and associated subscriber line. The supply voltage source assigned to the subscriber supplies an output voltage which is controllable as a function of a measurable variable.

Abstract: A telephone dialer for connection to a public switched telephone network (PSTN) and to a station apparatus, for receiving digits dialed from the station apparatus and for adding digits or substituting digits for the dialed digits and for redialing digits to the PSTN wherein the redialed digits are comprised of the dialed and added digits or comprised of substituted digits, the dialer further comprising an adjustable hold circuit for connection to the PSTN during an interval when the redialed digits are being output, for holding a line associated with the PSTN in an offhook condition, the adjustable hold circuit having a load connectable to the PSTN line which is variable with PSTN line voltage at the dialer such as to draw a variable current sufficient to meet predetermined current and voltage criteria of the line at the dialer.

Abstract: A doorbell response system in used in a dwelling including a telephone line and a telephone. The doorbell response system includes a doorbell, doorbell button, speaker, microphone, dialer to initiate the dialing of a telephone number, connection between the microphone and speaker, a system for eliminating the dial tone in the telephone line for a selected period of time so a person can communicate over the microphone and speaker, a system for dialing a number when the dialer is activated, a battery for the doorbell and doorbell button and telephone, and a trickle charge from the telephone line to the battery.

Abstract: A system and method for remotely powering an Ethernet network repeater through an attachment unit interface (AUI) between the repeater and a remote personal computer (“PC”) or workstation. The AUI includes logic circuitry to detect when the Ethernet is supporting a transmit signal and a receive signal. Associated with the AUI is a DC to DC converter which receives, remotely through the AUI interface, a DC voltage from the PC or workstation and converts the DC voltage into working voltages for the remote repeater.

Abstract: A digital isolation apparatus for coupling between a telecommunication network and a digital signal processing device. A CODEC is arranged to couple to the telecommunication network, convert a first set of analog signals from the telecommunication network to a first set of digital signals, and convert a second set of digital signals to a second set of analog signals to the telecommunication network. A digital isolation device, arranged to connect between the CODEC and the digital signal processing device, pass the first set of digital signals from the CODEC to the digital signal processing device, and pass the second set of digital signals from the digital signal processing device to the CODEC. A power supply assembly supplies power to the CODEC via the digital isolation device.

Abstract: A CMOS implementation for a DC holding circuit in direct access arrangement (DAA) circuitry is disclosed that provides desirable inductive behavior while minimizing power dissipation required by the CMOS integrated circuit, particularly at high loop currents. The DC holding circuitry disclosed may include MOS transistors located on a CMOS integrated circuit and an off-chip power dissipating resistor that acts to dissipate power external to the CMOS integrated circuit. The CMOS implementation disclosed also allows a path for drawing DC current to power other CMOS circuits (e.g., ADCs and DACs) in the CMOS integrated circuit.

Abstract: The communication system disclosed herein allows for the hookswitch devices to draw loop current from the phone line in both on-hook and off-hook conditions. Thus, even though an on-hook condition occurs, current may be obtained through the hookswitch devices. This feature allows circuitry which operates during on-hook conditions to still receive power from the phone line. Moreover because the hookswitch devices are utilized for drawing power in both on-hook and off-hook conditions, the use of additional switches dedicated to drawing the power during on-hook conditions is not required. For example, loop current may be drawn from the phone line through the hookswitch devices to power circuits used to perform the on-hook caller ID function. The powered circuits may include for example analog to digital converters. The technique disclosed herein for drawing current through the hookswitch devices is particularly useful for communications systems which utilize a capacitive isolation barrier system.

Abstract: A power feed circuit provides power for a telephone subscriber loop connected to a unit of terminal equipment. The power feed circuit includes a first current supply circuit for supplying power to the subscriber loop when the unit of terminal equipment is in an on-hook condition and when the unit of terminal equipment is in an off-hook condition, and a second current supply circuit for supplying power to the subscriber loop only when the unit of terminal equipment is in the off-hook condition. Each current supply circuit includes a respective battery, transistor and bias network. The first current supply circuit is connected to the subscriber loop via a diode which is reverse-biased when the unit of terminal equipment is in the on-hook condition. The power feed circuit may be usefully applied in an Optical Network Unit (ONU) of a "fiber-in-the-loop" telephone system or in a Subscriber-Cable Interface Unit (SCIU) of a cable telephony system.

Abstract: In a method and an arrangement for controlling the operating mode of a subscriber line interface circuit by mode control signals from a control circuit which is connected to the subscriber line interface circuit, the subscriber line interface circuit includes at least one latch which is interconnected between the control circuit and the subscriber line interface circuit. The latch is adapted to latch the mode control signals received from the control circuit in response to latch enable signals received from the control circuit, and to apply those latched mode control signals to the subscriber line interface circuit to control its operating mode.

Abstract: A telephone-system interface circuit connected to a central office via a tip line and a ring line includes a battery having a first terminal and a second terminal. A first current control circuit is connected between the tip line and the first terminal of the battery. A second current control circuit is connected between the ring line and the second terminal of the battery. The first current control circuit and the second current control circuit are equal in structure.

Abstract: A technique for powering telephone lines using an unbalance current source and current sink; and a technique for improving attenuation/frequency distribution and return loss (impedance matching) of transformer-coupled wire-line communications circuits by using secondary series capacitance and an AC current pump signal source; and a generation of ringing voltage as positive voltage pulses with respect to a negative power supply voltage; and a technique for removal of AC power ripple by using an active linear floating filter for the purpose of powering telephone line circuits, and a technique for injection of real time tone samples into T1 transmissions circuits by use of a T1 framer idle code register.

Abstract: An analog telephone subscriber terminal apparatus with means for realizing additional functions is provided. In the on-hook state of the subscriber terminal apparatus, and outside of the idle operating state of the subscriber terminal apparatus, a current supply device that draws current from the subscriber line and is integrated into the terminal apparatus is switched effective for the duration of the reception of data containing the additional functions. The current supply device provides the supply current to the means for realizing the additional functions, but is limited to such an extent that the increased subscriber line loop current that then flows is not indicated as a loop closure.

Abstract: A subscriber line interface circuit ("SLIC") for a telecommunications device powered from a single power source and using a voltage regulator to limit the voltage across the terminals of the telecommunications device to a predetermined value below the industry standard voltage limits. The SLIC selectively enables or disables the speech amplifiers responsive to an external control signal that is independent of the on-hook/off- hook status of the telecommunications device. The SLIC provides a ringing signal and/or a caller identification signal through the speech amplifiers to the telecommunications device while the telecommunications device is on-hook.

Abstract: In a telecommunication system, more particularly for the range of ISDN technology, which includes a switching device (1), a telecommunication terminal unit (19) coupled to the switching device (1) via a first number of bus lines (3, 4, 5, 6), and (9, 10, 11, 12) for providing phantom power supply to the telecommunication terminal unit (19) via the first number of bus lines (3, 4, 5, 6), user communication means including actuation switches (28) and indicator lamps (29) are coupled to the telecommunication terminal unit (19) via a second number of bus lines (14, 115, 16, 17). This enables simplified telecommunication with minimum circuitry and cost. Power is supplied to the communication means (28, 29) by the telecommunication terminal via the second number of bus lines (14, 15, 16, 17).