Abstract: A protection circuit for a cellular telephone battery includes a first memory for storing battery identification data and a second memory associated with the telephone includes data relating to which battery type may be used by this telephone. When the battery is connected to the telephone, the battery identification data is compared to the battery type data stored in the telephone. The battery is automatically disconnected from the telephone if the two sets of data do not correspond to each other.

Abstract: A system and method for providing on-demand battery backup to cable telephony devices comprising converting AC main power to DC power 102, charging a battery 104, providing regulated power to the cable modem device 106, detecting the presence of AC main power 108, providing a signal to the cable modem device to indicate that AC main power is not present 110, detecting said signal by said cable modem device 112, entering sleep mode and disabling said telephony interface 114, exiting sleep mode and enabling a telephony interface by said cable modem device upon activation of said cable telephony device 116, and signaling telephony service availability by said cable modem device 118.

Abstract: In a subscriber line interface circuit, a device applies to a line, associated with the line interface circuit, a substantially constant line current of a first predetermined value for line voltages up to a first voltage having an absolute value which, by a predetermined amount, is lower than the supply voltage of the line interface circuit. For line voltages between the first voltage and a second voltage having an absolute value which, by a predetermined amount, is higher than the first voltage, a line current which is inversely proportional to the line voltage and of a value between said first predetermined value and a second predetermined, lower value is applied to the line. For line voltages between the second voltage and a third voltage having an absolute value which, by a predetermined amount, is higher than the second voltage, a substantially constant line current of the second predetermined value is applied to the line.

Abstract: A method of managing power at an element management system for a power sourcing network element and a power sinking network element of an access network is provided.

Abstract: A method for controlling a line-powered network element in an access network is provided. The method includes provisioning at least one instance of a line power controller at the line-powered network element, provisioning at least one conductive medium associated with the at least one instance of the line power controller, receiving at least one primitive for use by the line power controller for managing the line-powered network element, monitoring at least one of the at least one primitive, and selectively taking action through the at least one line power controller based on the monitored ones of the at least one primitive in response to power conditions for the line-powered network element.

Abstract: An apparatus and method for maintaining access to lifeline services through telephone sets provided with telephone service from a voice over digital subscriber loop (VoDSL) transceiver during power interruptions are described. All telephone sets associated with the transceiver are connected to a wire loop which supports the VoDSL service in the event of a power interruption to the transceiver. The advantage is the economical provision of lifeline service access to all telephone sets when power is interrupted to the transceiver. Thus, confusion is reduced, safety is enhanced, and access to lifeline services is ensured during emergency situations.

Abstract: Terminals are connected via cables in a star-shaped fashion with respect to a HUB in a LAN. Each of the cables includes therein signal lines and power feed lines. The HUB includes therein a power feed section. The power feed section and the power feed lines of each cable are connected to measure a value of current which flows in the power feed lines. If it is judged based on the measured current value that the terminal connected to the corresponding cable is a telephone terminal, the power feeding to the corresponding power feed lines is continued. On the other hand, if the terminal is judged to be a terminal other than the telephone terminal, the power feeding is stopped.

Abstract: The invention relates to a monolithically integrated telephone circuit for driving wide-band telephone lines and transmitting digital data at a very high frequency. The telephone circuit is powered from a battery DC supply providing a pair of voltage references. The telephone circuit includes an output circuit portion including a pair of differential output stages, each having a pair of inputs and being connected with its output to a respective lead of a two-wire telephone line. The telephone circuit also includes a device for deriving a reference voltage from the supply voltage, and includes a low-voltage supply network which is input a DC signal and produces a voltage reference to be added to the reference voltage for delivery to one input of each output stage. The other input of each stage receives an AC signal in order to present at the circuit output a suitable AC+DC differential voltage for driving the telephone line.

Abstract: A line powered data access arrangement (DAA) is disclosed which adaptively allows proper operation with power supplied from a telephone line as conditions warrant, while at the same time satisfying the relevant requirements of many countries. In the line powered codec, a startup procedure for the international line powered codec uses register settings, e.g., country-specific register settings, which are powered and maintained from the low voltage side (e.g., from the PC or modem side) of the line powered codec. In this way, even during low line power conditions the programmed state of the line powered codec can be maintained, thus a default condition will not necessarily returned to by the line powered codec upon reset due to a power loss in the telephone line. In another aspect, a charge storage device such as a charge capacitor is charged from a charge pump formed from a differential clock signal from the low voltage side.

Abstract: A method and apparatus is provided for adjusting DC feed control of a connection. The method includes receiving a signal from the connection and determining if the change in the signal is greater than a first preselected value. The method further includes adjusting the DC feed in response to determining that the change in the signal is greater than the first preselected value.

Abstract: A comparator-based switchmode power converter monitors the most negative of the tip and ring line voltages, to control the supply voltage to a SLIC. The voltage applied to the SLIC's power terminals is slightly higher than the sensed voltage for different loop signaling conditions, including loop start, ground start balanced ringing. The switchmode converter includes a comparator coupled to a DC-DC output node downstream of a MOSFET switch installed in a DC supply rail of a source of DC supply voltage, and coupled to a power supply terminal of the SLIC. The comparator is also coupled to a set point node, which is coupled through a voltage offset path to each of tip and ring portions of the telephone line.

Abstract: A digital device for controlling the DC line current on a telephone line which includes a digital device that utilizes a digital filter for setting the DC line current. By controlling the DC line current digitally, software can be used to set the DC line current in accordance with predefined characteristics. Predefined characteristics can be set to accommodate varying country specifications instead of using switches to control resistors and capacitors. In addition, changes in a country's requirements can be accomplished through software, instead of changing components or redesigning a circuit board. The device also incorporates a method for maintaining DC current level during changes in digital filter characteristics. The use of software results in increased flexibility by allowing an infinite number of settings via software or software updates, and allowing changes to be made quickly and easily throughout the world.

Abstract: A device for remote line powering in a telecommunication network in which electric power is supplied via a plurality of line pairs and aggregated to provide electric power suitable for powering an appliance. The electric power supplied via each of the line pairs is adapted not to exceed a pre-defined threshold.

Abstract: A subscriber loop interface circuit and method for externally programming the on-hook, off-hook, and transition states of the subscriber loop interface circuit. The circuit having an off-hook overhead sufficient for long loop applications and having a continuous loop current to loop voltage relationship. The circuit may have plural means for generating reference currents for comparison with loop currents.

Abstract: A circuit configuration is provided for supplying a telephone subscriber loop with a supply voltage, for transmitting a transmitted signal into the telephone subscriber loop, and for receiving a received signal from the telephone subscriber loop. The telephone subscriber loop has a first line and a second line. The circuit configuration has a supply voltage source with a first terminal and a second terminal between which a supply voltage drops; a first circuit connected with the first line and having first and second supply voltage connections; and a second circuit connected with the second line and having third and fourth supply voltage connections. The first supply voltage connection is connected with the first terminal and the fourth supply voltage connection is connected with the second terminal. A network-side terminal of a telephone subscriber loop and a chip set are also provided.

Abstract: A system and method for distributing power over a premises network is provided. The system comprises a power receiving module operable to be coupled to a premises network located in a user site. A power source module is operable to be coupled to the premises network and a power supply. The power source module is operable to receive electrical power from the power supply and provide electrical power over the premises network such that the power is contained within the premises network.

Abstract: A circuit and supplemental power source connection scheme for a telecommunications modem transmission link are described. The supplemental power source is connectable at any point along a telecommunications wire, including the terminals of repeaters and remote terminals. The combiner circuit includes a diode bridge for ensuring the proper connection of externally connected high voltage power to internal circuitry of the power combiner. The combiner also includes a line polarity matching circuit that automatically configures to signally connect internal positive and negative voltage signals to corresponding positive and negative external signal lines on a telecommunications modem transmission link.

Abstract: A line terminal circuit comprises a buffer section (A, D) for connection to a transmission line (TL) and for performing at least one of the functions receiving signals from said transmission line and transmitting signals via said transmission line; a controllable current source section (S1, S2) connected to inject or withdraw a current (Iu, Id) into or from a node (ND1, ND2) between said buffer section and said transmission line in accordance with a current control signal (CS); and a common mode voltage control section (CT) for detecting a common mode voltage component on the transmission line (TL) connected to the buffer section (A, D) and for generating said current control signal (CS) in response to said detected common mode voltage component and outputting said current control signal to said current source section (S1, S2); said common mode voltage control section (CT) being adapted to output said current control signal (CS) such that said common mode voltage component is within the limits of a predetermi

Abstract: An isolation system for terminating a phone line is provided. The invention may comprise a capacitive isolation barrier across which a digital signal is communicated. 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. 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. A bidirectional isolation system is provided whereby bidirectional communication of digital signals is accomplished using a single pair of isolation capacitors. In preferred embodiments, the digital data communicated across the barrier consists of digital delta-sigma data signals multiplexed in time with other digital control, signaling and framing information.

Abstract: Transmitting a pre-recorded announcement to the user of an network interface unit (NIU) each time the user places a telephone call if an alarm is set because a battery in an uninterruptible power supply (UPS) is in a low power state. The pre-recorded announcement states that the battery needs to be replaced. The user is given a simple procedure for contacting service personnel at a service center to have the battery replaced in the UPS. In addition, this announcement is overridden if the user starts to dial the emergency telephone number (911). This allows the user to gain immediate access to the emergency telephone number without having to listen to the message stating that the battery in the UPS needs to be replaced. An indicator is also set on NIU upon the battery being in the low power state. If a call is completed to the service center, the alarm is reset for a predetermined amount of time to give the service personnel time to service the battery.

Abstract: A digital subscriber loop modem arrangement is arranged to respond to a fault condition so as to provide at least a voice lifeline service over DSL service on a digital subscriber line in which data and voice traffic are transported on a plurality of carriers. On detection of a power loss at the subscriber end of the line, the number of carriers is reduced so as to maintaining transmission only of those carriers transporting the voice traffic. This reduces the power demand which can now be met from the remote end of the line. A method of operating a digital subscriber loop modem arrangement under a fault condition so as to provide at least a voice over DSL service on a digital subscriber line in which data and voice traffic are transported on a plurality of carriers, the method comprising the steps of: replacing the data with random data, disabling those data carriers on which the random data is transported, and maintaining transmission of those carriers transporting the voice traffic.

Abstract: A communication system is provided with a power supply budget such that portions of a phone line side circuit may be powered from the TIP and RING phone lines while using standard electronic devices for the hookswitch circuits and the diode bridge circuit. For example, low voltage converters in the phone line side circuit may be powered from the phone line. The low voltage converters may operate off a low voltage power supply of approximately 2.5 V or less, more preferably may operate off a low voltage power supply of approximately 2.0 V or less, and in one embodiment 1.9 V converters may be utilized. The communication system may further include a capacitive isolation barrier system for isolating the phone line side circuitry.

Abstract: A system for managing power from a power source for at least one line powered network element in an access network is provided. The system includes a power manager that establishes at least one power criterion for the at least one network element. Further, the system includes a power controller that is responsive to the power manager. The power controller and the power manager communicate to manage operation of the at least one network element based on the at least one power criterion.

Abstract: The feeder circuit to which the present invention pertains comprises means for regulating which serves to feed an electric current to a positive output terminal and a negative output terminal; means for feeding electric current which serves to feed an electric current to the means for regulating; means for regulator control which serves to control the electric current output from the means for regulating; a first resistance located between the negative terminal of the means for feeding electric current and the positive output terminal; and a second resistance located between the positive terminal of the means for feeding electric current and the negative output terminal.

Abstract: A power management circuit for a remote access platform extracts power from a wireline for powering a ring generator that generates a ringing voltage signal that is distributed to a plurality of subscriber circuits. A power-limited voltage converter steps up the wireline voltage to a higher ‘isolating’ voltage, charging a capacitor coupled to the ring generator. A monitor circuit reduces the power that the power-limited voltage converter can draw, if the wireline voltage drops too low. This prevents the wireline voltage from collapsing should the remote terminal be deployed at a distance from wireline voltage source (the central office) greater than its specified capability.

Abstract: The disclosure discloses a method for extending the length of time over which a cordless telephone system can operate without an external source of power. The method involves detecting a power supply outage, determining that a telephone call is not currently being handled, placing the portable unit into a mode of reduced power consumption, and placing the base unit into a mode of reduced power consumption. After a period of time, the base unit resumes functionality, determines whether a call is being initiated, and handles any such calls. If the system is not active, the base unit re-enters its mode of reduced power consumption, and the cycle is repeated.

Abstract: An uninterruptable power supply for use with an Internet Telephone or Internet Telephone Cable Modem comprises a power supply and a load. The power supply has an AC/DC converter for producing converter DC, and also a rechargeable battery. A DC output multiplexer selects one of such DC sources and furnishes it to the load. The multiplexer has an input control signal for switching the DC source to a battery, and an output indicator indicating when the battery is acting as the DC source. The load includes a controller which generates this test signal at times when it is useful to test the battery, and accepts the indicator signal to know when the battery is providing this current. The controller includes a test function for measuring the reserve charge of the battery by measuring the temporal voltage drop and time of this temporal voltage drop with the use of an A/D converter. Additionally, the controller measures the charge and discharge intervals of the battery.

Abstract: Battery operated devices can be redesigned to use a cordless telephone battery. A battery back-up system that uses a battery for battery operated devices is also presented. Also included is an adapter to change the type of connecter on a cordless telephone battery.

Abstract: A load management system for monitoring the output from a power supply and managing the load on said power supply, said load management system comprising a hysteresis circuit for signaling a load element to stop drawing current when an output voltage at said output falls below a first threshold and for signaling said load element to resume drawing current when said output voltage rises above a second threshold, said hysteresis circuit comprising a first state sensing circuit having an input coupled to said output and for signaling whether said output voltage is greater than or less than said first voltage threshold, a second state sensing circuit having an input coupled to said output and for signaling whether said output voltage is greater than or less than a second voltage threshold, and a state transition circuit having a first input coupled to the output of said first state sensing circuit and a second input coupled to the output of said second state sensing circuit, said state transition circuit having a

Abstract: A processor controlled mechanism automatically determines from a location such as a central office whether termination equipment installed at a remote end of a wireline link is span-powered, or is powered locally. It then applies a voltage to the wireline link that is appropriate for the identified type of termination equipment. This eliminates the need for two separate central office loop-powering devices. In the course of making the determination, nothing higher than a safety extra low voltage is applied to the wireline link, to comply with Underwriter's Laboratory standards for locally powered customer premises equipment.

Abstract: A power switch device is used with a telephony instrument that is connected to a local phone loop via two telephone wires and that has two power lines for connection to a power source. The device includes a rectifier connected to the telephone wires, and a latching relay having an exciting coil connected to the rectifier via a differentiator, and a switch unit. The coil is excited by current flowing through the differentiator when a ring signal is present at the telephone wires so as to enable the switch unit to make connection between the power lines and the power source. An integrator is connected between the rectifier and the coil, and discharges when neither the ring signal nor a talking signal is present at the telephone wires so as to excite the coil and enable the switch unit to break connection between the power lines and the power source.

Abstract: A line card for coupling to customer premises equipment at a termination for detecting hook condition in a telephone system, the line card comprising an interface for transmitting and receiving an analog signal with the telephone line, an AC ring signal generator for generating a ring signal at the customer equipment, a DC signal generator for generating a DC signal when said customer equipment is off hook, and a circuit for determining the duty cycle of a loop current in the customer equipment (telephone) for determining the hook status of the customer equipmen.

Abstract: A subscriber circuit is capable of realizing a CLIP service in an old-fashioned switching system. The subscriber circuit has a ringer transmitting circuit, which is connected to line A and line B, and which transmits a ringer signal in accordance with a ringer transmission request signal from a host system; a battery feed circuit, which supplies speech current to line A and line B; and a timer, which detects, in accordance with a change in the level of a ringer transmission request signal from the above-mentioned host system, the end of transmission of a ringer signal transmitted by the ringer transmitting circuit, starts timer operation, and ends this timer operation after a predetermined time has elapsed. The battery feed circuit supplies speech current to line A and line B from the above-mentioned battery feed circuit during the operation period of the timer.

Abstract: A power management system is interfaced with both a local utility power source and a remotely powered span, and monitors the power availability for and requirements of DDS terminal equipment. Upon detecting that local utility power is insufficient to operate the terminal equipment, a power limited converter derives power from the phone line. The span power drawn is limited to a fixed value that prevents the line from collapsing. An auxiliary capacitor stores energy from either local utility power or the span, to provide for periods of extended power operation (including ringing the phone).

Abstract: A method and an arrangement supplies power in a communications network (100) comprising subscriber side (110) and a provider side (120), the provider side being connected to nodes of the subscriber side through one or more Line Terminals (LT1, . . . , LTn) and at least one equipment (111-114) at the subscriber side (110) being connected to the provider side (120) through at least one Net Terminal (NT). The arrangement comprises apparatus for supplying power to the communications network (100) at least during a period of time through the at least one Net Terminal from the at least equipment (111-114).

Abstract: The object of the present invention is to provide a subscriber line interface device in which a spacing factor and feeding efficiency of the low-voltage power supply are improved. The subscriber line interface device according to the present invention is capable of feeding a plurality of subscriber terminals connected thereto, with different voltages, characterized in that it includes a (low) voltage power supply distributed to a plurality of subscriber line interface boards, each capable of connecting to a predetermined number k of the subscriber terminals, in order to feed with a voltage (for example, −30 VDC), the absolute value of which is lower than that of a maximum voltage (for example, −48 VDC) among the different voltages.

Abstract: Method and apparatus for alternately providing positive and negative direct current voltages to a single twisted pair includes a power source configured to provide a first signal and a second signal, the first and second signals having different polarities, a controller configured to provide a control signal in accordance with a predetermined timing signal, and a voltage alternating switch circuit having first and second output terminals, the voltage alternating switch circuit coupled to the power source configured to receive the first and second signals, the voltage alternating switch circuit further coupled to the controller configured to receive the control signal, and in accordance thereto, providing first and second signals alternately to first and second output terminals, such that the adverse corrosive effect of positive voltage line powering is minimized.

Abstract: A surge reset circuit used to automatically reset a surge protection circuit within a telephone line interface circuit. A sensor (e.g., a zenering device) advantageously generates a voltage level representing current draining out of the transient voltage suppression portion of the surge protection circuit after a transient energy surge. If the current is draining, which may indicate a potential lockup situation, feedback circuitry generates a reset feedback signal that is provided to a cutoff device. The cutoff device, in response to receiving the feedback signal, disables a current limiter portion of the surge protection circuit to reduce the current draining from the transient voltage suppression portion. As the current level is reduced, the transient voltage suppression portion will reset when the current drops below a threshold value or is substantially eliminated. As a result, the feedback circuitry removes the reset feedback signal from the cutoff device to re-enable the current limiter.

Abstract: The invention relates to a MOS transistors substitutive circuit having a transformer/data interface function, in particular for ISDN networks, comprising first (11a) and second (11b) power supply/transmitter blocks, the first power supply/transmitter block (11a) being connected between a voltage reference (V) and a first data interface (RX), and the second power supply/transmitter block (11b) being connected between a ground potential reference (GND) and a second data interface (TX), both power supply/transmitter blocks being connected to a supply voltage reference (VDD). The MOS transistors substitutive circuit according to the invention comprises first (12) and second (12′) MOS transistor pairs connected to the voltage reference (V), the MOS transistors being diode configured and held in their saturation range, so as to have a high A.C. impedance and virtually zero D.C. impedance, thereby minimizing power dissipation through the substitutive circuit.

Abstract: An improved system and associated components for providing reliable power supply and interconnectivity for digital subscriber line (DSL) applications at sites remote from the central office (CO). The system comprises a line power unit in communication with a subscriber-installable gateway module, the latter incorporating a power extraction circuit adapted to extract power from the Telco line. Home phone network (HPN), homeplug, and wireless modules are also provided within the gateway to permit connectivity between other electronic components within the subscriber's site. Subscriber-installable adapter modules which extract power and perform line interface functions for the various jacks throughout the site are also disclosed. Methods for installing and operating the aforementioned components are also described.

Abstract: A battery and component monitoring and notification device for a garage door operator is shown that provides telephone or internet notification when back-up batteries or other components require replacement. The device uses a programmable information processor to monitor the condition of back-up batteries or other components, actuates a telephone line interface to dial out a stored telephone number, and then actuates a voice control chip to play a stored telephone message. The telephone number and message are inputted by the user. The device may also provide notification over the internet by telephone line or other internet connection system. In addition, the device uses one or more battery chargers that each operate in one of two charging modes depending on the level of charging current to each battery.

Abstract: Line circuits can be supplied with a first voltage or a second voltage of a lower absolute value. At least the second voltage is variable. The line voltages of at least active line circuits are measured, and possible values for the second voltage are prognosticated. It is determined which line circuits can be supplied with the respective possible value, and the power consumption of those line circuits is calculated using each possible value. For the line circuits which cannot be so supplied, the power consumption is calculated using the first voltage. For each possible value prognosticated for the second voltage, the total power consumptions are summed, and the value that gives the lowest total power consumption is selected as the second voltage. The line circuits are then supplied with the first voltage or the selected second voltage.

Abstract: A telephone system includes a transmission line for connection to at least one telephone and a telephone interface in communication with the transmission line. The telephone interface provides DC power when a telephone connected to the transmission line is in an off-hook state. A controller in communication with the telephone interface generates a pre-defined DC characteristic of the telephone interface, and a regulator in communication with the controller adaptively translates the DC characteristic.

Abstract: A system (150) for controlling voltage supplied to a transmission line system. System (150) includes a transmission cable (134) having a characteristic impedance and a load impedance connected at its distal end. A power source (154) is connected to transmission cable (134). Power source (154) is configured to receive a voltage signal input (157) and to drive a source voltage VS based thereon. A feedback unit (155) is configured to receive the power source current (IS) as an input and further configured to generate a feedback voltage (VF) that varies with IS. A set voltage unit (152) is configured to produce a substantially constant voltage (Vset) and an adder (153) is configured to add the set voltage (Vset) to the feedback voltage to generate the voltage signal (157) that provides the input to power source (154). The feedback unit (155) may include an impedance element (156) comprising a digital signal processor or other suitable circuit that models the short circuit impedance of the transmission line.

Abstract: A telephone line interface circuit is disclosed that functions with use of PTC resistors so that temperature increases within the battery feed resistors is minimized. Utilizing current and voltage feedback loops within the line interface circuit, the PTC resistors are implemented without significantly reducing the performance of the overall circuit that would normally be caused by the PTC resistors' inherent impedance inaccuracies. In normal operation, the feedback loops adjust the current and voltage on the telephone line to the desired level without regard for the impedance values of the PTC resistors. In the case that a high voltage is applied to a telephone line, the significant increase in current flow into the line interface circuit causes the battery feed resistors to heat up, and therefore the PTC resistors, that are physically local to the feed resistors, to heat up and significantly increase in impedance.

Abstract: Telecommunications carrier equipment in a field cabinet can be replaced so as to allow existing carrier multiplexers to be powered by newer, smaller power supply equipment. Each carrier multiplexer has a plurality of power connections for each of a plurality of power types. The existing set of power supply equipment has a supply connection corresponding to each power connection at each power types. The power inputs of each power type for each carrier multiplexer are bridged together. A replacement set of power supply equipment has a single supply connection corresponding to each power type for each carrier. Each of the bridged power inputs for each carrier multiplexer is connected with the corresponding supply connection on the replacement set of power supply equipment for each power type.

Abstract: To reduce power losses in a SLIC comprising first and second current amplifiers supplying line current to respective wires of a two-wire transmission line to a load, a line current detector detects line currents below a threshold value. For line currents above the threshold value, the second amplifier is supplied from a first battery with a substantially constant voltage. A voltage regulator is connected with its output terminal to the second amplifier, with its current supply terminal to a second battery of higher absolute voltage than said first battery, and with its input terminal to the detector. In response to line currents below said threshold value, the detector outputs control signals proportional to the detected line currents to control the output terminal of the voltage regulator to supply the second amplifier as well as the load from the second battery.

Abstract: To provide an information terminal device capable of automatically switching a plurality of power source applying paths depending on circumstances.

Abstract: In the occurrence of a data modem establishing a data communication session over a telephone line, a method is disclosed for detecting the modem and subsequently reducing the telephone line current. Initially, when a new telephone call is begun, the line current is set as normal to a current sufficient to power a standard telephone handset. Subsequently, using modulation detection techniques, it is determined whether a modem data session has been initiated on the particular telephone line. If such a session has begun, the normal current level on the telephone line is unnecessary since data modems are locally powered. To minimize wasted power and reduce thermal problems caused by the modem dissipating the excessive current, a reduced current is set on the telephone line. This reduced current is either a predetermined modem current level or a minimum allowable current for the particular telephone line, as calculated within the line interface circuit.

Abstract: A telephone line current amplifier comprises a current amplifying device comprising a first, second and third amplifier connected in cascade. The current from the third amplifier forms the output current of the current amplifying device. The current from the first amplifier subtracts from the current provided by the third amplifier, and the current from the second amplifier operates as a rectifier and outputs its current onto a power supply terminal. The power supply terminal is decoupled from ground via a capacitor. Another embodiment of the telephone line current amplifier comprises only two amplifiers if less severe distortion ratios are imposed.