Abstract: A transmitting device and a receiving device are coupled together via an interconnect. An electrical idle ordered set is received at the receiving device power management unit after having been transmitted by the transmitting device and received at the input pins of the receiving device and moving through the receiver logic pipeline. At the time the electrical idle ordered set has been recognized at the end of the receiver logic pipeline, the power management unit checks for activity on the interconnect. If there is no activity on the interconnect, then the power management unit causes the receiving device to enter a low power state where the receiver circuitry (input buffers) is turned off. If there is activity on the interconnect when the electrical idle ordered set is received at the power management unit, then the power management unit does not cause the receiver circuitry to be turned off.

Abstract: Systems and methods are provided for switching between power supply rail voltages for a differential driver device of a class G amplifier device. The amplifier device employs power MOSFETs to switch between supplying high supply voltages and low supply voltages to the power rails of the differential driver. The class G amplifier can be employed in driving an ADSL signal over a telephone line. A control device ramps the power supply rail voltage between low power supply states and high power supply states to mitigate noise and spikes that can be coupled to the output signal.

Abstract: A method and an apparatus provide for determining whether a data terminal equipment (DTE) device represents a compatible device lacking an independent power supply and adapted to be powered using phantom power over a wired connection from a communications device such as a switch. A detection signal may be transmitted from the communications device to an identity network connected to the DTE. A response detection signal may be returned and checked in a receiver at the communications device. A switch may then be closed to provide phantom power if the result of the check indicates that the DTE is a compatible device adapted to receive phantom power. Compatible DTE device may include telephones, Voice over IP (VoIP, IP or Ethernet) telephones, network access devices, computers, and the like.

Abstract: A half duplex device and signal processing method thereof. First, a signal detection unit of a signal detector of a half duplex device obtains a short-term power and long-term power. Next, a data update unit of the signal detector sets a short-term power threshold as a default threshold, determines whether the long-term power is greater than the default threshold, sets the short-term power threshold value equal to the long-term power value if the long-term power value is greater than the default threshold value, and provides smooth performance in a noisy environment.

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 subscriber line interface circuit has a battery-powered, high voltage analog section, that drives tip and ring lines of a subscriber loop, and a mixed signal (low voltage and digital signal processing) section, that monitors and controls the high voltage analog section. An input signal receiving unit of the high voltage analog section conditions input voice and low voltage signaling and ringing signals from the mixed signal section, for application to a dual mode, programmable gain, tip/ring amplifier coupled to the loop. A sense amplifier at the output of the tip/ring amplifier is through an auxiliary amplifier to an analog feedback monitor port for closing a loop to synthesize the circuit's output impedance.

Abstract: A method for generating power signals within a telephone server coupled to a computer system via an interface bus or in-house power connector, to a maximum number of telephones, and to a telephone trunk, the computer system providing a primary voltage signal and a secondary voltage signal, includes receiving the primary voltage signal and the secondary voltage signal from the computer system, generating a ringer power signal in response to the primary voltage, generating a direct inward dialing power signal in response to the primary voltage, the direct inward dialing power signal configured to provide a first operational power signal for telephones from the maximum number of telephones receiving telephone calls directly from the telephone trunk, generating a second operational power signal in response to the primary voltage for telephones from the maximum number of telephones receiving telephone calls from other telephones from the maximum number of telephones, and generating a ringing signal in response to

Abstract: According to an embodiment, a DC driver circuit is coupled to a tip/ring line. The DC driver circuit includes a first capacitor coupled to a first switch where the first switch is coupled to an amplification circuit. An RC circuit is coupled to a second switch where the second switch is coupled to the amplification circuit. During a make state, the first and second switches are closed, causing the amplification circuit to draw current from the tip/ring line. During a break state, the first and second switches are open, preventing the amplification circuit from drawing current from the tip/ring line. The transition from the make state, during which a significant amount of current is drawn from the tip/ring line, to the break state, during which no current should be drawn from the tip/ring line, occurs at a rate that results in a significantly reduced voltage peak at the tip/ring line.

Abstract: The present invention discloses a method and apparatus for reducing the power required by an integrated services hub supporting a plurality of telephone circuits, comprising offsetting ringing of each of the plurality of telephone circuits such that all the telephone circuits do not ring simultaneously. The step of offsetting ringing of each of the plurality of telephone circuits preferably further comprises providing each telephone circuit with a ring cadence comprising a ringing interval and a non-ringing interval and defining a starting point for the ringing interval within each telephone circuit's ring cadence such that the starting point for the ringing interval for at least one telephone circuit falls substantially outside the ringing intervals of the remaining telephone circuits.

Abstract: A method and apparatus is for providing a phantom battery feed to reduce power consumption in a differential amplifier circuit. A voltage signal is driven onto a telecommunications line using a first amplifier and a second amplifier. A phantom battery feed is performed during a negative cycle of the voltage signal. Performing the phantom battery feed comprises: supplying a negative supply terminal of the first amplifier with a supply voltage that is one-half of a full scale supply voltage; and supplying a positive supply terminal of the second amplifier with a supply voltage that is one-half of the full scale supply voltage.

Abstract: A ring boost circuit has a first switching device coupled to a ring node. The first switching device is responsive to a ring operation. A charge pump is connected to the ring node, and the charge pump provides a voltage offset to enhance a differential voltage between the ring node and a tip node when the first switching device is activated during the ring operation.

Abstract: In the case of the inventive telephone, telephone operating signals (bell signal, charge-unit signals and caller identifiers) and audio signals are processed together by an integrated circuit. This requires signal level matching to be performed for the individual signals. Since the telephone signals are processed together by a chip, preferably by a digital signal processor, the hitherto required complexity for discrete components can be reduced.

Abstract: In a method and apparatus for data transmission and voice signal transmission on a subscriber line, in terminal devices located at least on a network side of the subscriber line, only those parts which evaluate a criterion indicating the beginning of the data transmission are switched into active mode outside the context of data transmission.

Abstract: A circuit for exchanging communications via a transmission line, including a detector for detecting a predetermined start-of-communication signal, a means for coupling the transmission line on the one hand to a transmit line to provide outgoing communications to the transmission line, and on the other hand to a receive line, to receive incoming communications from the transmission line. The detector is connected to the transmit line.

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: An apparatus and method for enabling Cisco legacy power to support IEEE 802.3 AF standard power. A network power system capable of delivering data terminal equipment power via a media dependent interface includes power source equipment according to Cisco legacy power and at least one powered device according to IEEE standard power. A power compatibility module is inserted between the power source equipment and the powered device to enable the power source equipment to appear according to IEEE standard power and the powered device to appear according to Cisco legacy power. The module includes switches, a DC/DC converter, an IEEE power source equipment circuit, and an isolator. The module optionally includes a user signaling device for communicating operating conditions of the module to a user. The module may be connected to two ports of the power source equipment to supply adequate power levels to the powered device.

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: An apparatus for receiving a voice signal and data, and a controlling method thereof, by which a voice telephone call can be made even in power failure, network error, or CPU error, comprises: a splitter for dividing data transmitted from a data transmission unit into an internet protocol data packet and a voice signal; a first telephone connected to an analog POTS channel of the splitter for receiving the voice signal divided in the splitter; and an integrated access device (IAD) for connecting a second telephone to a voice line, that is, the analog POTS channel of the splitter or connecting the second telephone to a data line of the splitter according to state of power failure.

Abstract: To achieve an improved convergence behaviour for, e.g., echo cancellation there is provided a digital adaptive filter which includes a filter coefficient update means to successively update filter coefficients in accordance with an input signal, an estimated power of the input signal, and an error signal between the input signal filtered in the digital adaptive filter and the input signal propagated along an external path being modelled by the digital adaptive filter. Here, an input signal power estimation means is adapted to perform recursive smoothing for an increasing input power and a decreasing input power in an asymmetric fashion with different smoothing factors. In case the estimation is carried out in the frequency domain the step size for the update of filter coefficients may be calculated for each frequency band individually.

Abstract: A telephone comprises an acoustic alarm, conversation members, first control means for the acoustic alarm, second control means for the conversation members, first supply means and second supply means for absorbing energy from a telephone line, the first supply means and the second supply means supplying the first control means in a call condition and the second control means in a conversation condition, respectively, wherein the first supply means further supplying the second control means in the call condition.

Abstract: A novel physical layer transceiver is provided for receiving data transmitted via residential wiring. The transceiver includes an input circuit for receiving an incoming pulse signal, and an energy detector responsive to the incoming pulse signal for producing a pulse energy value representing energy of the incoming pulse signal. An adaptive energy detector gain control circuit is responsive to the pulse energy value for adaptively controlling gain of the energy detector so as to maintain the pulse energy value at a predetermined level. The gain of the energy detector is controlled in response to at least one of access identification pulses preceding data pulses to identify the transmitting station. The adaptive energy detector gain control circuit includes a comparator for comparing a pulse energy value produced by the energy detector with a preset threshold level, and a controller for supplying the energy detector with a gain control value.

Abstract: A line card or other telephone or communications interface provided with a ringing SLIC outputs relatively high voltage, such as in excess of about 90 volts, and/or relatively high current such as in excess of about 20 milliamps during normal use, but decreases the voltage or current of a ringing signal or other signal upon occurrence of a tip and/or ring line fault or other abnormal condition. The abnormal condition is detected by measuring voltage and/or current on the tip line and/or ring line. In response to an excess voltage or current, the ringing current or other output current is reduced to achieve desired safety and/or compliance with standards.

Abstract: A bidirectional amplifier circuit includes first and second input ports, first and second output ports, a power amplifier, and first, second, third, and fourth filter circuits. The power amplifier includes at least first and second input terminals and first and second output terminals. The first filter circuit is coupled between the first input port and the power amplifier first input terminal. The second filter circuit is coupled between the second input port and the power amplifier second input terminal. The third filter circuit is coupled between the first output port and the power amplifier first output terminal. The fourth filter circuit is coupled between the second output port and the power amplifier second output terminal. Carrier waves of differing frequencies may be injected into the amplifier circuit first and second input ports, and transmitted from the first and second output ports.

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: Method and apparatus for providing a regulated and current limited power source to support bidirectional telephone delivery circuitry and methods for a multiplicity of telephone subscriber lines to a downstream distribution terminal using only two preexisting transmission lines for carrying the regulated and current limited power along with a multiplicity of HDSL TDM communication channels.

Abstract: An overcurrent protection circuit for an analog modem which uses passive-device features during normal operation to minimize modem signal noise and distortion, and active-device features when inadvertently connected to a line having excessive line current.

Abstract: A message transmission system having at least one subscriber's terminal device that is connected by way of a subscriber's line that is comprised of a first and second lead, with a subscriber's interface circuit (SLIC), preferably integrated, which comprises a loop detector circuit and subscriber's feeder circuit, such that in the area of, or on the subscriber's terminal device, a subscriber signaling display is provided, which may be controlled by way of a signaling control circuit, and such that a controllable switch (8) is connected between the subscriber's interface circuit (3) and the first lead (a) of the subscriber's line (a, b), which switch, in a first position, connects the first lead (a) of the subscriber's line (a, b) and an input of the subscriber's interface circuit (3) with each other, and in a second position, connects the first subscriber's line lead (a) with a pole of an additional power source (5).

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: The stage includes two channels each connecting an input to an output. Each channel includes a first device for adding to the input voltage of the channel concerned a feedback voltage from the other channel to the channel concerned. For remote power feeding a terminal, the stage further includes respective means in each channel for adding a DC voltage to the output voltage of that channel. The feedback voltage is a function only of the AC component of the output voltage of the first device of the channel concerned. Application to telephone exchanges.

Abstract: The invention creates a method for adjusting a ringing signal current in a subscriber line (106), a ringing signal generator (114) which generates the ringing signal being connected with one end of the subscriber line (106) and at least one subscriber (102) being connected to another end of the subscriber line (106), comprising the steps of detecting a ringing signal current of the ringing signal; of comparing the detected ringing signal current with a predetermined current value; and when the detected ringing signal current is greater than the predetermined current value, reducing a ringing signal voltage of the ringing signal in such a manner that the ringing signal current is equal to the predetermined current value, the ringing signal voltage being dropped across the subscriber line (106) and a load of at least one subscriber (102). The invention also creates a circuit arrangement for carrying out the method.

Abstract: In a telephone system employing a PBX server to communicate with local telephones over a local area network, fallback adapters are provided to automatically respond to a power failure and also respond to the failure of the PBX server to automatically connect the telephones directly to a telephone line. This automatic connection enables the telephones to be used as analog phones and make and receive calls directly without using the PBX server. Power failure is detected by relays which default to a position to connect the telephones directly to the telephone line. The fallback detectors have controller logic which detects the presence of a ringing signal on the telephone line and the failure of the PBX to respond to the ringing signal. In addition, the fallback detectors detect the failure of the PBX to respond when a telephone is used to attempt to make an outgoing call or a call to another one of the local telephones.

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: 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 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 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 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: A circuit provides a modulation signal to an input terminal of a line modulator which places a line current modulated in accordance with the modulation signal on a telephone line. An amplifier of the circuit amplifies an analog input signal to provide the modulation signal at an output terminal. A first resistor and a first capacitor are coupled in series between a first input terminal of the amplifier and the line, and a second resistor and a second capacitor are coupled in series between a second input terminal of the amplifier and the line. First and second precharge amplifiers are used to precharge the first and second capacitors, respectively, to reduce DC setup time.

Abstract: Driver circuit for at least one subscriber terminal, comprising a first driver (14) for amplifying the power of a direct-voltage signal applied for supplying power to the subscriber terminal, the first driver (14) being supplied by a first supply voltage (V1), and comprising a second driver (37; 37a, 37b), following the first driver, for modulating high-frequency signal currents onto the power-amplified direct-voltage signal.

Abstract: In a splitterless xDSL communications services set-up providing data and voice services to co-connected equipment, data signals may cause audible interference in POTs handsets. The degree of the interference varies widely due to a wide variation of customer tolerance and of susceptibility of the handsets. Reducing data channel transmission power during an off-hook event may reduce interference. A method and system are provided for user adjusted cutback. While making a POTs call, data channel power may be adjusted until acceptable performance is obtained. The customer selected power cutback influences both ATU-R and ATU-C transmit levels.

Abstract: A telephone apparatus and method for stabilizing a call in a no power operation (NPO) mode. A sub-controller controls the NPO mode by at least one of a central office line voltage and an external supply voltage, and a main controller performs a booting operation in response to the external supply voltage to control an operation of the sub-controller under the condition that the external supply voltage is provided. A power-on detector detects a power-on state to output a power-on detection signal to the sub-controller, whereupon, during a call connection in the NPO mode, the sub-controller outputs a booting hold or reset signal to the main controller to prevent the main controller from booting a program masked in an internal ROM area. A hook-on signal based on a hook-on state of a handset, causes the sub-controller to block the output of the hold or reset signal, enabling the main controller to perform the booting operation after a call termination occurs.

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: The line interface circuit of a modem to be connected to a standard RJ11 jack of a digital PBX (Private Branch Exchange) is used along with software routines resident in the modem to detect the presence of a PBX connected to the modem. Upon going off-hook, the modem, by the software routines, determines whether the connection will harm the interface by one of several software routines. If it appears that the interface circuit may be damaged because a PBX line is present, the modem is instructed to go on-hook (hang up), or if the connection is not harmful to the interface, alerts the user that the modem is connected to a wrong jack.

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 in which a programmable DC current limiting mode is available. In the current limiting mode, power may be dissipated in devices external to a DAA integrated circuit. Moreover, much of the power may be dissipated in external passive devices, such as resistors. Further, the current limiting mode includes a distortion adjustment circuit to limit distortion at a crossover point at which current limiting effects occur.

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 is a second order circuit. The use of a second order circuit provides improved distortion characteristics, particularly at low frequencies.

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 in which a programmable DC current limiting mode is available. In the current limiting mode, power may be dissipated in devices external to a DAA integrated circuit. Moreover, much of the power may be dissipated in external passive devices, such as resistors.

Abstract: An adapter (42) for connecting a telephone (52) to a telephone wire (40) has a subscriber line interface circuit (SLIC 113) with a jack for connecting a telephone to the SLIC, a line interface (110) for coupling to a telephone line, a signaling circuit (111) coupled to the line interface for receiving and providing subscriber line signaling on the telephone line, a codec (112) coupled to the SLIC, performing a voice coding/decoding function; and a timing circuit (202) for time multiplexing and demultiplexing of digitized voice signals between the SLIC and the line interface.

Abstract: A telephone test set is protected from an excessive current condition by a protection circuit that maintains sufficient loop current flow for continuous operation of the telephone equipment's functional circuitry, while by-passing and/or reducing excess current that could potentially damage the protected circuitry. A series current-limiting element is installed in the loop current path between a tip and ring interface and the circuitry of the telephone test set. A current shunting circuit is installed across the tip-ring ports of the protected circuit downstream of the current-limiting element. A current sense circuit monitors the loop current and controls the operation of the shunting circuit in accordance with the magnitude of the loop current. If a substantial overcurrent condition persists for an extended period of time, the resulting power dissipation associated with the high current flow will cause the current limiting element to change to a high impedance state.

Abstract: A transmission power control device is provided for controlling transmission power of a transmission signal, so that interference between transmission signals to a plurality of mobile stations is reduced. The transmission power control device of the present invention comprises a total transmission power monitoring section 1 for monitoring total transmission power being transmitted to a plurality of mobile stations by a base station and outputting a monitor signal, a target total transmission power setting section 2 for calculating a total transmission power value applicable to a base station and outputting a setting signal, an adder 3, a multiplier 4, an adder 5, a delay circuit 6, a limiter 7, a desired SIR setting section 8 and an adder 9.

Abstract: A pay telephone unit is disclosed that derives all operating power from the tip and ring conductors of the telephone line without the need for a battery. All data is stored in nonvolatile memory requiring no power for data retention, even when disconnected from the telephone line. The unit employs an interrupt architecture that advantageously reduces current consumption in comparison with prior art polling arrangements. In addition, stored power from operational circuitry is diverted to keep the real-time clock operating during momentary disruptions in line power. Diverted power may also be used to permit certain parameter settings, when initiated by the real-time clock, to be changed while the telephone unit is in an on-hook condition.