Abstract: An office-line trunk circuit is provided to selectively operate on ground-start and loop-start modes. In this circuit, a DC current detection circuit has (i) a first photo coupler detecting a DC loop current caused responsively to supply of the ground to a tip line and a negative power to a ring line from an office bilateral trunk and (ii) a resistor whose resistance is adjusted to prevent a loop start in the office bilateral trunk and allow DC current to be detected. The first photo coupler detects the loop current using the resistor. An incoming detection circuit has a second photo coupler detecting a ring signal coming from the office bilateral trunk. A DC sink circuit has a diode bridge placed between the tip and ring lines and configured to have a DC circuit provided with a transistor controlling the DC loop current so that the office bilateral trunk is allowed to selectively be loop-activated and loop-held.

Abstract: A ring detect circuit is shown that includes a regenerative latch configured to be coupled to a telephone line. The regenerative latch is configured to generate a fast transient signal in response to a ring signal on the telephone line. The latch is coupled to an isolation transformer through a capacitor. The fast transient passes across the capacitor and through the transformer. A comparator detects the fast transient and, responsive thereto, generates a ring detect signal.

Abstract: In one aspect, a data communication system includes a modulator, an integrated acoustic data coupler, and a demodulator. The modulator modulates a carrier signal having a frequency in an operating frequency range in response to an input data signal and provides the modulated carrier signal at a modulator output. The integrated acoustic data coupler includes an acoustically resonant structure that has one or more acoustic resonant frequencies in the operating frequency range. The acoustically resonant structure includes a first thin film electro-acoustic transducer electrically coupled to the modulator output, a second thin film electro-acoustic transducer, and a substrate. The substrate supports, acoustically couples, and provides an electrical isolation barrier between the first and second thin film electro-acoustic transducers.

Abstract: Various methods, apparatuses, and systems are described in which devices having no common electrical ground communicate. In at least certain embodiments, an apparatus includes a transformer block to communicate a plurality of data signals and a synchronous clock signal between a first device with a first ground reference and a second device with a second ground reference over a data communication link. The first device sends the plurality of data signals to a modulator block having one or more Boolean logic gates that receive each data signal in combination with the synchronous clock signal. The modulator block sends a plurality of modulated data signals corresponding to the plurality of data signals to the transformer block. The transformer block sends the plurality of modulated data signals and the synchronous clock signal to the second device to provide the data communication link between devices having different ground references.

Abstract: A system and method are presented for interfacing multiple plain old telephone system (POTS) devices with multiple cellular devices in communication with a cellular network to enable efficient communication among these devices. In a broad sense, the system includes an interface configured to function as a bridge between the POTS devices and the cellular devices. The interface selectively routes call attempts from a POTS device to one of a group of cellular devices which connect the calls from the POTS device over the cellular network. The interface may be configured to detect a key sequence for selecting a particular cellular device in the group during an outgoing call attempt from the POTS device. The interface then routes the outgoing call to the selected cellular device. The interface may also be configured to detect a telephone number entered into the POTS device during an outgoing call attempt and route the outgoing call to a particular cellular device based on criteria pre-programmed in the interface.

Abstract: A method for qualifying a telephone line for very-high-bit-rate digital subscriber line (“VDSL”) service is disclosed. Generally, a telephone line for VDSL service is prequalified based on a length of the telephone line. A VDSL rate of the telephone line is measured and it is determined whether to qualify as VDSL data qualified based on the measured VDSL rate and a VDSL rate threshold. A VDSL video quality of the telephone line is measured and it is determined whether to qualify the telephone line as VDSL video qualified based on the measured VDSL video quality. Finally, a network database is updated with the determined VDSL data and video qualifications of 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 circuit for the DC termination for a variety of international phone standards. The invention may also be utilized with circuitry 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: A facsimile apparatus, to which an external telephone enables to be connected through a line, has a line I/F section that transfers and receives signal through a network, a voltage detection section that is provided in a semiconductor DAA and detects a line voltage of the line, an adjustment section that adjusts a line voltage during establishment of a connection through the line so as to be within a predetermined voltage, and an external telephone monitor section that acquires a value of the line voltage detected by the voltage detection section at regular time intervals and monitors a use state of the external telephone based on the acquired values of the line voltage.

Abstract: Methods and apparatus for coupling outgoing analog audio signals to a subscriber line are described. One method includes the step of receiving the outgoing audio signal. The outgoing audio signal is coupled to the subscriber line through a plurality of transistors coupled in a common base configuration. In one embodiment, linefeed driver control signals for controlling battery feed to the subscriber line are received on the same signal lines as the outgoing audio signal. A subscriber line interface circuit apparatus includes a first circuit for coupling a received outgoing audio signal to a subscriber line. The first circuit couples the received outgoing audio signal to the subscriber line through a common base isolation stage. In various embodiments, the common base isolation stage comprises a plurality of bipolar junction transistors coupled in a common base configuration or a plurality of field effect transistors coupled in a common gate configuration.

Abstract: An improved ADSL system with improved data rate is disclosed. In one embodiment, the upstream data bit rate is increased by extending the upstream transmission band. In another embodiment, the downstream data is also increased by extending the downstream transmission band.

Abstract: The invention concerns a digital signal distributing installation comprising a first coupler to be connected to an ADSL line input and to an electric power distribution line, an ADSL modem with a first and a second port, and a second coupler to be connected to the first port of the modem and to the electric power distribution line. Said installation is enhanced by adding thereto an auxiliary electric power distribution line, and a filtering circuit interposed between the electric power distribution line and the auxiliary electric power distribution line.

Abstract: A subscriber line interface circuit apparatus includes a linefeed circuit and a subscriber line control circuit (SLCC). In an embodiment, the linefeed circuit includes a signal conversion circuit which provides a differential mode signal and a common mode signal in response to at least a tip signal and a ring signal from the subscriber loop. The linefeed circuit includes a tip control circuit and a ring control circuit. In an embodiment, the SLCC is provided in a single integrated circuit chip and is coupled to the linefeed circuit which isolates the SLCC from the tip or ring signals. The SLCC includes a first and a second differential mode inputs for receiving the differential mode signal, and a common-mode input for receiving the common-mode signal. In an embodiment, the SLCC also provides various tip control signals and ring control signals to the tip control circuit and the ring control circuit, respectively.

Abstract: A system for generating, delivering and distributing electrical power to network elements over a data communication network infrastructure within a building, campus or enterprise. Consolidating power distribution and data communications over a single network simplifies and reduces the cost of network element installation and provides a means of supplying uninterrupted or backup power to critical network devices in the event of a power failure. The invention includes power/data combiners that combine a data communication signal with a low frequency power signal. The combined signal is transported over the LAN infrastructure where a power/data splitter extracts the data signal and the power signal and generates two separate outputs. The power over LAN system of the present invention operates with high bandwidth data communication networks, i.e., 10 Mbps, 100 Mbps, 1000 Mbps.

Abstract: A splitter unit including a chassis containing splitter cards. The splitter unit includes a central processing unit mounting location. The splitter unit also includes test access devices that are inactive when the central processing unit mounting location is vacant. The splitter unit is configured such that the splitter cards provide passive signal splitting even when the central processing unit mounting location is vacant.

Abstract: An ADSL POTS splitter includes low pass filter. The low pass filter includes a first inductor portion in communication with the line interface and a second inductor portion isolated from the line interface via an isolation capacitor. In one embodiment, the first inductor portion is characterized for non-saturation in conventional operating ranges. The first non-isolated inductor portion has a respective DC saturation current and the isolated inductor portion has a respective DC saturation current. The DC saturation current of the first non-isolated inductor portion is substantially greater than the DC saturation current of the isolated inductor portion for achieving higher inductance in the isolated inductor portion.

Abstract: A hybrid circuit that decouples gains for a transmit signal and a receive signal of a broadband modem that is coupled to a telephone line is provided. The hybrid circuit includes a multi-port transformer, a pair of line matching resistors, and a bridge circuit. The multi-port transformer includes a line coil electrically coupled to a telephone line, a linedriver coil magnetically coupled to the line coil and a receive coil that is also magnetically coupled to the line coil. In an alternate embodiment, a hybrid circuit is provided that includes a multi-port transformer in which the line coil, linedriver coil and receive coil include two coil segments. A broadband modem incorporating a hybrid circuit of the present invention is also provided.

Abstract: In order to provide unbalanced ringing when an exchange line card provides a balanced ringing output the interface provides a ringing detector in circuit with a customer pair. On detecting balanced ringing signals from the line card, the interface takes over the customer line pair and provides unbalanced ringing signals to the customer and monitors for customer answer. By inserting the interface in circuit at the main distribution frame of an exchange, legacy customer premises equipment which is unable to respond to balanced signalling can be provided with an appropriate ringing signal without the necessity to provide differing line cards at the exchange.

Abstract: The present invention relates to a transceiver for bidirectional frequency division multiplexed transmission, a communication system including one or more transceivers. Optionally, the communication system is a communication system for a digital subscriber line. The transceiver comprises transmission means with a voltage source output or a current source output for transmitting data in a transmission frequency range, receiving means for receiving data in a receiving frequency range, and a coupling impedance for connecting the transmission means and the receiving means to a transmission medium. The magnitude of the coupling impedance in the transmission frequency range is smaller than the magnitude of the coupling impedance in the receiving frequency range if the transmission means has a voltage source output and is higher than the magnitude of the coupling impedance in the receiving frequency range if the transmission means has a current source output.

Abstract: The invention relates to a transmitter for transmission of digital data via a transmission line (10), comprising a current-driving digital/analogue converter (1) which is arranged at the input of the transmitter; a current-operated form filter (2) for forming the current pulses which are supplied from the digital/analogue converter; a line driver (5) which carries out current/voltage conversion; and a circuit for offset compensation (6), which is arranged in a feedback path (11). In order to improve the quality of the pulses which are transmitted at the output of the transmitter, the invention proposes that the internal signal processing of the transmitter be carried out on a current basis.

Abstract: A method includes the step of providing subscriber loop pull-down circuitry operating in a first voltage domain. The subscriber loop pull-down circuitry decreases at least one of a tip and a ring line current in response to a corresponding pull-down control signal. The method further includes the step of providing control circuitry operating in a second voltage domain, wherein the first and second voltage domains are substantially distinct. The control circuitry varies the pull-down control signal to decrease a selected one of the tip and ring line currents in response to a sensed current corresponding to an associated one of a tip pull-down current and a ring pull-down current. A subscriber line interface circuit apparatus includes pull-down circuitry operating in a first voltage domain. The pull-down circuitry varies line currents of the tip and ring lines in response to a pull-down control signal provided by control circuitry operating in a second voltage domain.

Abstract: An electronic signaling device and a loop system incorporating at least one of the devices is described. The device is powered by the loop current and voltage and includes circuitry which enables it to function both in the mode where loop current is interrupted and when it is not. Each device has its own unique ID which is interrogated by the circuitry and which includes further circuitry for interrupting the loop current so that the unique ID can be transmitted to a remote location. Circuitry is provided to determine whether or not other loop activity is taking place before the device transmits its ID. Pause circuitry is provided to create distinguishable intervals between each digit of the ID and between each, successive transmission of a complete ID. Shut down circuitry is provided to return the device to its quiescent state after it has transmitted its ID or when an anomaly occurs.

Abstract: A high efficiency line driver is disclosed. The line driver may be applied with equal advantage in wired and wireless communication media to amplify data signals with a minimum of power consumption. In an embodiment of the invention a line driver is disclosed which includes: at least one amplifier, a delay element, a control signal generator and a generator. The at least one amplifier includes at least one bias supply, a signal input and a signal output. The delay element accepts as an input the data signal and delays delivery of the data signal to the at least one line amplifier for amplification. The generator is responsive to a control signal to generate varying voltage levels corresponding thereto on the at least one bias supply of the at least one amplifier. The control signal generator is responsive to the input data signal to detect peaks therein and to generate the control signal corresponding thereto in advance of delivery of the data signal to the amplifier.

Abstract: A method and an apparatus for upgrading an existing service outlet (e.g. LAN, telephone, power or CATV outlet) in a house by adding functionality thereto. The functionality is added by an add-on module, connected electrically and secured mechanically to the existing outlet. Several attachment devices are exampled, including surface attachment, side clamping, snap locking, strap securing and fastening screws. The add-on module may include a service connector for retaining the basic existing outlet function. The module may be attached in a permanent way or by using a detachable solution.

Abstract: A method and network device increases the power of the signal transmitted by the device on a wired communications network, such as a powerline communications (PLC) network, without exceeding the maximum allowable common-mode (CM) current specified by regulatory bodies. The device is first tested for regulatory body compliance on a standard network. The output voltage of the device is adjusted until the maximum allowable CM current is detected, and this voltage level and CM current are recorded and stored in non-volatile memory of the device. The device is then connected to the actual network and the output voltage set to the previously recorded value. At this voltage level, the CM current in the actual network is measured and recorded.

Abstract: A system and method for delivering digital subscriber line (DSL) service to a subscriber from a remote terminal of a telephone network. Included is a first route for delivering a telephone signal to the subscriber, and a second route for passing the telephone signal through a DSL system before delivering the signal to the subscriber. A disrupter is then used to selectively activate either the first or second route.

Abstract: An extender circuit for handling a communication signal transmitted over a transmission line includes a voltage clamp and a current booster circuit. The voltage clamp is connected to a receive end of the transmission line and is operable to clamp a reflection signal caused by the communication signal received at the receive end of the transmission line. The current booster circuit is connected to the receive end of the transmission line and is operable to provide a boost current at the receive end of the transmission line during a positive transition of the communication signal.

Abstract: A subscriber line interface circuit apparatus includes a first driver for driving a downstream data signal in a non-voiceband range and a metering signal onto a subscriber line. The apparatus includes a second driver for driving a downstream voice signal in a voiceband range onto the subscriber line. Receiver circuitry is coupled to provide an upstream data signal and an upstream voice signal from an upstream signal carried by the subscriber line. The first driver and receiver circuitry reside on a same first integrated circuit die.

Abstract: A method is provided that can be used for modifying a control parameter associated with a digital subscriber line (DSL) service. Initially, a real-time performance parameter is received from a first termination unit that is coupled to an DSL circuit. The real-time performance parameter is measured at the termination unit after the termination unit is provisioned and after the DSL circuit is placed in-service. A value of a control parameter associated with the DSL circuit can be modified based on the measured real-time performance parameter. Further, activity over the DSL circuit can be monitored in real-time and when usage of the DSL circuit is below a threshold, the provisionable service parameter that corresponds to the control parameter is modified. Moreover, a first re-provisioning cycle between the first termination unit and a second termination unit coupled to the DSL circuit can be initiated using the provisionable service parameter.

Abstract: A switchable transmission device for the VDSL CO/CPE circuit is disclosed. A new hybrid filtering means is used to integrate a CO transmission set and a CPE transmission set into a single device. A switching unit is in charge of switching the functions. A VDSL controlling unit of the preferred embodiment operates the integration of the filtering function between the CO or the CPE transmission sets, and a CO/CPE circuit switching unit operates the circuit switching. After that, the filtered signal is transmitted to an output circuit filtering unit, and outputted via a communication port connect unit subsequently. Furthermore, a status displaying unit displays the operation status of the device. The switchable transmission device for the VDSL CO/CPE circuit can efficiently combine the LANs through existed telephonic copper wires.

Abstract: A digital subscriber line communicating system having a central office and a remote terminal connected through a telephone line, the transmitting side including a sliding window transmitting unit for transmitting DMT symbols according to the sliding window through the telephone line to the receiving side, and the receiving side including a sliding window receiving unit for receiving DMT symbols according to the sliding window from the transmitting side, the sliding window indicating the phase of cross-talk condition due to a TCM-ISDN transmission at the receiving side, whereby TCM cross-talk can be reduced without largely departing from the standard system.

Abstract: A network device comprises first and second transceivers configured to aid communication between a plurality of networked devices; first and second communication medium connections in communication with the first and second transceivers, and capable of receiving first and second communication media, respectively; and a sliding door, said sliding door retained between an upper sliding track and a lower sliding track such that said sliding door covers one of said first and second connection while exposing the other of said first and second connection.

Abstract: A line driver comprises a driving amplifier receiving an input of the line driver, a current sense resistor connected between the driving amplifier output and the line driver output, and a feedback amplifier sensing the voltage across the current sense resistor and providing a corresponding feedback voltage that is proportional to the output current to the driving amplifier, thereby determining an output impedance at the line driver output. Precise output impedance can be realized by using a high precision resistor as the current sense resistor, and using resistive feedback amplifiers with accurate gains as the driving and feedback amplifiers. The resistance of the current sense resistor can be substantially less than the line driver output impedance, and the driving amplifier output voltage swing can be substantially less than twice the line driver output voltage swing.

Abstract: A subscriber line interface circuit apparatus includes a controller for controlling a DC feed of a subscriber loop in accordance with a first DC feed curve defined by a first set of points in response to sensed subscriber loop signals. A stability compensator is coupled to the subscriber loop. The controller maps the first set of points to a second set of points to define a compensator-adjusted DC feed curve for compensator-affected sensed signals received from the subscriber loop. The controller controls the DC feed in accordance with the compensator-adjusted DC feed curve in response to compensator-affected sensed subscriber loop signals such that the subscriber loop DC feed follows the first DC feed curve.

Abstract: A method for selecting a profile for a digital subscriber line is disclosed, the method including collecting code violation data for a plurality of digital subscriber lines, identifying a group of problem lines in the plurality of digital subscriber lines, modeling estimated code violations for each of a group profiles for each line in the group of problem lines and selecting one of the group of profiles. A system is disclosed for performing the method.

Abstract: A subscriber line interface circuit apparatus includes a signal processor having sense inputs for a sensed tip signal and a sensed ring signal of a subscriber loop. The signal processor generates at least one linefeed driver control current in response to the sensed signals. The signal processor is not a predominant source of any of a tip current or a ring current of the subscriber loop.

Abstract: A subscriber line transceiver apparatus includes an integrated circuit coupling at least one of an upstream and a downstream voice path for carrying voice signals to a subscriber line. The integrated circuit couples at least one of an upstream and a downstream data path for carrying data signals to the subscriber line. The voice signals are communicated within a first frequency range and the data signals are communicated within a second frequency range. The first and second frequency ranges are distinct.

Abstract: A subscriber line interface circuit apparatus includes driver circuitry for combining and driving a downstream voice signal and a downstream data signal onto a subscriber line. Receiver circuitry receives and separates an upstream signal from the subscriber line into an upstream voice signal and an upstream data signal. The driver and receiver circuitry reside on a common integrated circuit die.

Abstract: A subscriber line interface circuit apparatus includes a first driver for driving a downstream data signal in a non-voiceband range onto a subscriber line and a second driver for driving a downstream voice signal in a voiceband range onto the subscriber line. The apparatus includes receiver circuitry coupled to provide an upstream data signal and an upstream voice signal from an upstream signal carried by the subscriber line. The first driver and receiver circuitry reside on a same first integrated circuit die.

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 apparatus for offloading power includes a power offload element providing a supply drop from a first supply level to a second supply level. The supply drop varies in response to a control signal. A signal processor of a subscriber line interface circuit provides the control signal. A linefeed driver of the subscriber line interface circuit is coupled to receive the second supply level for driving a subscriber line.

Abstract: A method for providing spectral containment over telecommunications service lines is provided. The method includes selecting a filter having spectral characteristics corresponding to a predetermined passband. The method also includes connecting the filter in series to at least one loop used to provide at least one telecommunications service to a customer. The method further includes activating service over the at least one loop. The filter attenuates signals transmitted on frequencies outside of the predetermined passband over the at least one loop.

Abstract: Uninterrupted digital communications are provided between a central office and a customer premises by using a high-pass or bandpass filter to bypass local loop generation equipment. In many present-day telecommunications installations, local loop generation equipment may be placed in series with a communications path that runs between the central office and the customer premises. This communications path is adapted to convey digital signals as well as voice information and/or other types of baseband communications signals. In order to avoid interference between baseband signals and digital signals, each of these signals is allowed to occupy only a specified portion of the frequency spectrum. When activated, the local loop generation equipment breaks the entire communications path, interrupting voice signals, as well as any digital signals which may be carried thereon.

Abstract: A method and system are provided for wiring a digital subscriber line circuit between a customer premises and a central office. A first connection for a first cable pair is established between the customer premises and a distribution frame in the central office. The first cable pair carries a full range signal from the customer premises to the distribution frame. A second connection is established at the distribution frame for a second cable pair between the distribution frame and a digital subscriber line access mulitplexer (DSLAM) in the central office for routing the full range signal from the first cable pair. A third connection is also established at the distribution frame for a third cable pair between the distribution frame and a voice switch in the central office for routing the full range signal from the first cable pair.

Abstract: The present invention provides, in one embodiment, a method of simplifying filtering with respect to a band plan. The method includes selecting a reflection point relative to the band plan and designating subchannels as unusable within a filterable separation of the reflection point that would otherwise introduce an asymmetry within the filterable separation. The present invention also provides a filtering simplifier for use with a DSL system having a band plan. The filtering simplifier includes a reflection point selector configured to select a reflection point relative to the band plan. The filtering simplifier also includes a subchannel designator coupled to the reflection point selector and configured to designate subchannels as unusable within a filterable separation of the reflection point that would otherwise introduce an asymmetry within the filterable separation.

Abstract: A Multiservice Access Concentrator (MAC) provides a time limit for a first ringing voltage signal in response to an attempted call. The call is attempted via a voice over packet-data-network system (VOPS), wherein the VOPS comprises voice over Internet Protocol (IP), voice over Frame Relay, voice over Asynchronous Transfer Mode (ATM), and voice over High-level Data Link Control (HDLC) network systems. Generation of the first ringing voltage signal is terminated upon expiration of the time limit. A control message is transmitted to terminate the attempted call, wherein the control message is transmitted via the VOPS.

Abstract: The present application provides a variety of exemplary embodiments, such as modem systems, modem devices, modem connectors, host connectors, communication systems and communication cards. For example, there is provided a modem device for use to enable a host to communicate over a communication line, wherein the host has a host connector. The modem device comprises a line side circuitry capable of interfacing with the communication line; and a digital isolation barrier (DIB) coupled to the line side circuitry, the digital isolation barrier capable of being connected to a modem connector for connection to the host connector, wherein the digital isolation barrier is capable of isolating the modem connector from the line side circuitry. Moreover, the line side circuitry may include a line side DIB interface for communication with the digital isolation barrier. Also, the modem connector may be connected to the digital isolation barrier via one or more lines.

Abstract: A method and apparatus that minimizes saturation caused by power transfer in a communication system transformer, such as a transformer found in a Power-over-Ethernet system. A magnetic flux imbalance causing saturation in the transformer is detected. A compensation current is injected into a winding to minimize the magnetic flux imbalance and saturation.

Abstract: A receiver to detect pulses on a home phone wiring network using envelope detection. The receiver comprises an integrating capacitor charged by a first current source responsive to a differential signal propagated on the wiring network, and discharged by a FET in combination with a second current source. The combination of the FET and the second current source allows the capacitor to be quickly discharged in a smooth fashion. An application of this receiver is for a PHY according to the Home Phoneline Networking Alliance.

Abstract: An apparatus comprising a first differential output driver to provide a single ended output voltage in response to an input voltage, a second differential output driver to provide a single ended output in response to the input voltage where the first output voltage and the second output voltage are representative of the positive and inverted input voltage. The apparatus also includes a feedback circuit to monitor the first and second output voltages and apply a bias voltage to at least one of the first and second output drivers to vary the point where the first and second output voltages cross-over as the input voltage changes from a first to a second level.

Abstract: A surge clamp circuit that may be implemented with DAA circuitry to limit the total voltage developed across one or more line side capacitors due to charge pumping phenomenon during a multi-transient events such as lightning strikes. The surge clamp circuit is capable of electronically sensing a transient event (e.g., lightning strike) and of momentarily turning on one or more components of a DAA hookswitch circuit during on hook mode to discharge the voltage developed across one or more line side capacitors before it reaches critical breakdown levels. The surge clamp circuit may be configured with a clamping sensitivity selected so that the DAA hookswitch circuitry is only activated or turned on upon occurrence of relatively large and potentially damaging transient events, and not upon occurrence of non-damaging transient events, such as operational signals.