Abstract: A telecommunication system has a supply circuit to supply power to a telecommunication line. The telecommunication line is connected to a telecommunications subscriber device. The supply circuit has a first electronic impedance that is connected between a first voltage reference terminal and a first wire of the line, and a second electronic impedance that is connected between a second voltage reference terminal and a second wire of the line. The first electronic impedance has a first transistor, and the second electronic impedance has a second transistor. The supply circuit further has a first impedance multiplying circuit with a third transistor, and a second impedance multiplying circuit with a fourth transistor. The first impedance multiplying circuit multiplies the impedance of the first electronic impedance, and the second impedance multiplying circuit multiplies the impedance of the second electronic impedance.

Abstract: A telephone headset interface circuit is coupled to a telephone line to extract power for use by a headset amplifier and is particularly adapted for use with telephone handsets having dynamic or electret microphones. The telephone line connects a telephone to a service system, such as a Central Office, a PBX system, or a Key system. The interface circuit includes a power extraction circuit having a plurality of circuit portions, each one coupled to a corresponding one of the telephone line wires for providing a predetermined output voltage, so that substantially identical electrical impedance characteristics are introduced to each such wire. An amplifier is coupled to the telephone handset such that the predetermined constant output voltage is coupled to the amplifier to power the amplifier from the telephone line when the telephone includes an electronic microphone handset.

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

Abstract: A ring generator circuit provides both a ring signal and talk battery to a subscriber telephone line. The ring generator recognizes whether talk battery voltage or a ring signal voltage is required and supplies the right voltage without the use of external relays. A switching network is coupled to the primary of a transformer to generate AC power at the transformer secondary. The switches intermittently conduct current from a DC power source through the primary of the transformer at a frequency substantially greater than the ring signal. A rectifier circuit converts the generated AC power into DC power to be provided to the telephone line. A sampling circuit samples the AC power, and the sampled power is additively combined with the DC power from the rectifier to form a ring signal component whose frequency is equal to the difference between the sampling frequency and the AC power frequency.

Abstract: A communication system is provided which draws virtually no loop current during a ringing burst and only draws on-hook loop current during the caller ID field. More particularly, ringer burst circuitry may be powered from the user powered circuitry by the transmission of power across the isolation barrier rather than being powered from the phone line. Thus, loop current need not be drawn from the TIP/RING lines during ringer bursts. The isolation barrier may be a capacitive isolation barrier which allows bidirectional communication and extraction of power from signals transmitted across the barrier.

Abstract: A fixed subscriber unit is connected to one or a plurality of wire telephones through wire and to a radio base station, which is connected to a public network, through radio to mediate communication between a telephone, which is connected to the public network, and the wire telephone. The fixed subscriber unit includes a supply state detection unit for detecting an electric power supply state from an external power supply. The fixed subscriber unit further includes a supply control unit for detecting reduction of a voltage supplied from the external power supply and a power failure on the basis of the detected result of the supply state detection unit, and setting a voltage supplied to the wire telephone to a value smaller than a rated voltage when the reduction of the voltage or the power failure is detected. The rated voltage is a voltage supplied to the wire telephone when the voltage supplied from the external power supply is normal.

Abstract: Protection circuitry for use with a modem is provided that detects excessive voltage between the tip and ring lines of a telephone subscriber loop when the modem is off-hook. When the over-voltage condition is detected, a switch is active, creating a circuit path that directs current away from the DC-holding circuit of the modem, thereby protecting the modem. The protection circuit of the present invention may be implemented using a minimal number of simple and inexpensive components.

Abstract: The present invention relates to a power supply circuit SC receiving a power supply current IS at an input voltage VLN and intended to supply a voltage VDD, comprisinga capacitance CS,a first transistor T1 enabling the capacitance CS to be charged by means of the power supply current IS,a second transistor T2 enabling said charge to be interrupted by diverting the power supply current IS to the reference terminal VSS, anda control module T3, T4 controlling the conductance of the first and second transistors T1 and T2 as a function of the values of the input and output voltages VLN and VDD.According to the invention, the power supply circuit SC also comprises a measuring module with which the value of the power supply current IS can be controlled.

Abstract: A circuit for monitoring battery voltages of a telephone terminal facility is disclosed. This circuit mainly includes a ringing detection circuit for generating a pulse signal in response to an off-hook signal or a ringing signal, a power detecting circuit for detecting battery voltages and a latch being in series connection with the power detecting circuit for outputting a signal showing a status of the detected battery voltages. The power detecting circuit and the latch are of an edge-triggered type and are activated only when a handset of a telephone is picked up or a ringing signal is received so that both the consumed power and the voltage variations are low.

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

Abstract: A subscriber circuit has several SLIC circuits (2, 3, 4, 5) combined in one multiple SLIC. The high-energy components of each SLIC circuit (2, 3, 4, 5) are realized as individual components (30, 31, 36, 37) in standard form. In order to remove non-linearities, the individual components (30, 31, 36, 37) are fed back via the respectively allocated SLIC circuit.

Abstract: A current-limiting circuit (110) of a battery-feed circuit (FIG. 1) for a digital telecommunications line (T,R) provides a low start-up current limit (I3) when power is initially applied to the digital line. It automatically and gradually changes (40) to a high current limit (I1) as the load on the line is charged. When the load is fully charged, the circuit provides a low impedance to the line. Upon occurrence of a fault, the circuit switches back to the initial low current-limit state. The circuit comprises a feed transistor (Q1, Q11), a control transistor (Q2, Q12), and a high-impedance resistive circuit (R1-R4, R15). The feed transistor limits (403) current flowing to the R lead of the line to the high limit when the voltage across the feed transistor is low (0-V2) and the feed transistor is saturated.

Abstract: A transmission power control method in an Asymmetric Digital Subscriber Line (ADSL) system for transmitting data through a telephone line interposed between an ADSL-TUC (Transmission Unit Center) and an ADSL-TUR (Transmission Unit Remote). The ADSL system compares a noise margin with a reference value and reduces a transmission power level of a transmission signal step-by-step, beginning from an initial maximum power level. When the transmission power level is reduced to the point that the noise margin no longer exceeds the reference value, the transmission power level is then restored to a level just high enough that the noise margin is greater than the reference value. As a result crosstalk is minimized while permitting optimum data transmission rates and saving transmission power.

Abstract: Methods and apparatus for using and/or switching to an auxiliary communication pathway to increase system reliability and/or reduce maintenance costs is disclosed. One feature is directed to a smart network interface device (SNID) implemented using latching relays. The SNID has very low power requirements and can be remotely controlled in a reliable manner through the use of simple tone signal commands over common POTS line pairs. Upon detecting a fault condition on a main line pair, the SNID is remotely instructed to disconnect the faulty line pair and switch the telephone customer's line connected to the faulty line pair to an auxiliary line pair. To operate in a POTS telephone environment without the need for an additional power supply, the SNID is designed to be powered from the power available from the auxiliary line pair. The power supply circuitry of the SNID is designed to have a near infinite input impedance with regard to input signals below twenty volts.

Abstract: A self-contained signaling and control device for detecting DTMF tones and generating a signal, such as an audible, visual, or control signal, upon detection of one or more predetermined DTMF tones includes an on/off-hook detection circuit coupled to a telephone line; a power supply circuit coupled to the on/off-hook detection circuit; a DTMF receiver circuit coupled to the power supply circuit; a logic circuit coupled to the DTMF receiver circuit; and a signal generator coupled to the logic circuit and the power supply circuit. The on/off hook detector circuit for detecting changes in voltage across a telephone line includes a circuit for detecting a voltage on the telephone line and a circuit for generating an enable signal in response to rapid changes in the voltage on the telephone line. The on/off hook detector circuit does not generate an enable signal in response to slow changes in the voltage on the telephone line.

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

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

Abstract: Terminal equipment for telecommunications and information processing with improved electromagnetic compatibility (EMC). The equipment has a human-machine interface (HMI), a metallic telecommunications interface (TCI), and optionally a power line interface (PLI). First common-mode rejection filters consisting of common-mode choke coils and shunt capacitors are placed at the HMI interface of the equipment, while second common-mode rejection filters consisting of the same components are placed at the TCI and PLI interfaces. High-frequency junction points of the first and second common-mode rejection filters are interconnected with a bypass circuit. Being isolated from the signal ground and frame ground of the equipment, the bypass circuit is an independent non-grounded circuit. Such internal structure makes it possible to reject noise signals induced by an external noise source and also to suppress spurious radiation from an internal noise source.

Abstract: A power converter forming part of a telephone subscriber line interface circuit selectively generates a ringing signal waveform, for supply to the line, or a supply voltage for a driver circuit for providing loop current on the line. First and second fixed frequency PWM signals are used to control the power converter, and hence the voltage which it generates, for the ringing signal waveform and the supply voltage respectively. The first PWM signal enables the power converter to provide a high power level needed for ringing signals. The second PWM signal has a lower frequency, and hence results in lower switching losses and power dissipation, and a lower duty cycle, suitable for the lower power level needed for the supply voltage, and is conveniently produced by masking pulses of the first PWM signal. The frequency of the second PWM signal is greater than 270 kHz, to avoid transmitting spectral energy to the line below this frequency.

Abstract: To determine the deviation of longitudinal signal components from a predetermined value on a balanced two-wire circuit (A,B), a first voltage is measured between one of the wires (A) and a first reference potential by means of a first voltage measuring means (3), a second voltage is measured between the second wire (B) and a second reference potential by means of a second voltage measuring means (4), and the difference between the first and the second voltage is formed by means of a difference forming means (5), said difference being proportional to the deviation of the longitudinal signal components from the mean value of the first and the second reference potential.

Abstract: Methods and apparatus for conserving power in terminal units that transmit and receive modulated data over a communications loop that is shared with voiceband telephone equipment are disclosed. The methods include monitoring the loop to detect a shut-down condition and reducing power consumption of certain of the electronic circuits in the terminal unit upon detection of a shut-down condition. The methods also include monitoring the loop with a monitoring circuit to detect a resume signal outside the voiceband frequency range on the loop and restoring power to the electronic circuits when the resume signal is detected. The apparatuses include a modulated data transmitting and receiving unit having a connector for coupling the unit to a communications loop, circuitry to transmit and receive a modulated data signal in a frequency range above voiceband, and circuitry to detect a resume signal in the frequency range above voiceband and then to initiate a power up sequence for the transmit and receive circuitry.

Abstract: A cellular communication system which eliminates high costs and difficulties associated with providing electrical power to the access points. The cellular communication system includes a remote power source which obviates the need to install an AC power outlet in close proximity to each access point. The remote power source transforms AC power to DC power at a central remote location, and provides as its output one or more low voltage DC power lines. By performing the AC/DC power transformation at a central location, only the low voltage DC power lines need to be fed to each access point. The remote power source also includes a backup power supply feature and an alarm to draw attention to system malfunctions.

Abstract: A data access arrangement generates a first current in a first current path which runs from a tip terminal of a line pair through a light emitting diode of an opto-isolator to a sense node. The data access arrangement also generates a second current in a second current path that runs from the tip terminal to the sense node. The first current is modulated in response to an audio input signal received from the telephone line pair, while the second current is modulated in response to a potential generated at the sense node, such that a third current flowing from the sense node to the ring terminal remains at a substantially constant predetermined magnitude.

Abstract: An electronic voice circuit configuration can be connected through a first and a second line terminal to a telephone line. The electronic voice circuit configuration has a calling part, a transmitting device, a receiver device, a symmetrical modulator circuit with voltage stabilization, a symmetrical equipment impedance device with a device for symmetry control and direct-current limiting, and a symmetrical control device.

Abstract: Power saving control apparatus and method for a simple electronic exchange system which may ensure the efficient system operation and reliably maintain the operation of the system by the usage of the electric power from an auxiliary AC power in consideration of battery power even after a main AC power is down.

Abstract: A line card integrates subscriber line interface circuitry, A/D and D/A converters, and digital signal processing technology. The digital signal processing technology performs many line card tasks such as switch hook detection, ground key detection, DC feed control, polarity reversal, ringing tests, fault detection, power cross detection, and ring trip detection. The digitally processed DC feed control ensures that digitally filtered A (Tip) and B (Ring) conductor voltages closely follow actual subscriber loop Vab voltages to avoid circuitry saturation and to validate power feed operating point calculations relative to actual subscriber loop conditions. Furthermore, the DC feed control opens a Vab fluctuation window in high current gain areas of subscriber loop power feed to reduce noise.

Abstract: A DC termination device particularly adapted for use in a device coupled to a two wire telecommunications system. The termination device controls the tip-to-ring current through the telecommunications device by means of a voltage controlled current source. The control voltage for the voltage controlled current source is provided by digital signal processing of the tip-to-ring voltage such that the tip-to-ring current is linearly proportional to the tip-to-ring voltage when the voltage is below a specified threshold level, but is maintained constant when the tip-to-ring voltage is over the threshold voltage. Preferably, the constant current is the minimum adequate current needed for operation.

Abstract: A communication apparatus has a power saving stand-by mode for reducing power consumption during stand-by and a non-ringing call receiving mode for communication without ringing an attached telephone set at the arrival of a call. In the power saving stand-by mode, an operation state of a relay for attaining the non-ringing call receiving mode is held by a stand-by power supply to render both modes compatible to each other.

Abstract: An improved network interface unit having a substantially smaller width than many prior art network interface units. The network interface unit comprises a single, planar circuit board assembly interconnected between incoming and outgoing telephone lines and incoming and outgoing customer premises lines. Two relays and a controller are mounted on the board. The controller monitors the transmission of data along the lines and, by activating the relays, provides communication and maintenance functions, such as loopback. The network interface unit utilizes a controller made up of (1) a processor-based software control system and (2) an integrally cooperating application specific integrated circuit. The controller may, for example, provide and monitor framing, detect and monitor signals, and convert bipolar data to unipolar data.

Abstract: A two-line subscriber system (10) includes a remote channel unit (20) coupled to a central office (14) by a single telephone line (16). The remote channel unit (20) provides additional line capability to a customer premises (18) by allowing a first telecommunications unit (22) and a second telecommunications unit (24) to operate despite having only a single telephone line (16). The remote channel unit (20) operates from a local power source (26), such as a battery or customer premises alternating current, to provide operating power to the first telecommunications unit (22) and the second telecommunications unit (24). In response to a loss of the local power source (26), the remote channel unit (20) cuts a connection to the second telecommunications unit (24) and passes line power from the single telephone line (16) to the first telecommunications unit (22) for continued operation of the first telecommunications unit (22).

Abstract: A standby feed circuit for a subscriber line comprising a constant current power feeding circuit for a subscriber line for supplying a voltage to a subscriber line at a voltage less than a standard central office power feeding circuit, a voltage source for providing the standard voltage, apparatus for applying the standard voltage when a station apparatus connected to the subscriber line is in an on-hook condition, and apparatus for applying said voltage less than the standard voltage in place of the standard voltage when the station apparatus is in an off-hook condition.

Abstract: High-speed digital transmission can be achieved with existing phone lines and HDSL chipsets while retaining plain old telephone service (POTS) with full failsafe capability. One original digital data signal ?4! at a rate of at least 352 kbps and typical 384 kbps and one POTS channel ?10! digitized at 64 kbps are multiplexed by a HPCS card ?6! of a signal provider ?1!. The resulting digital signal is transported over a twisted based on the current technology. At a receiving end, the signal is demultiplexed and regenerated by a subscriber's HPCS card ?7!. The subscriber's HPCS card is line-powered via the cable ?2! to avoid dependence upon local power. The regenerated signals are transmitted over one POTS line ?42! and one data line ?8! to or within a remote premise. Both HPCS cards have bypass relays for the POTS line to ensure the subscriber's POTS access in the event of a local power outage or electronic failure.

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

Abstract: A circuit for preventing data stored in a memory of a telephone system from being corrupted including: a memory for receiving a plurality of control signals from the processor and for storing received data; a decoder connected to a chip enable terminal of the memory, for receiving a plurality of control signals from the processor and for generating a memory enable signal during a normal operation voltage range of the processor, and for placing the memory in an inactive state by supplying a disabling signal to the chip enable terminal of the memory during an abnormal operation voltage range of the processor; a voltage sensing circuit, connected to a chip enable terminal of the decoder, for generating a high level during the normal operation voltage range of the processor, and for generating a low level during the abnormal operation voltage range of the processor for controlling the decoder; and a battery power source supplier for supplying power to the memory and the decoder.

Abstract: A communication system includes a SLIC device and a SLAC device. The SLIC device and the SLAC device cooperate to control the power level provided to a subscriber line. The SLAC device includes a digital control circuit which receives a parameter signal indicative of a first parameter of the electrical power. The digital control circuit provides a digital control signal to the SLIC device in response to a sample digital control signal and the digital parameter signal. Preferably, the digital parameter signal relates to a sensed current signal and the sample digital control signal relates to a desired voltage signal. The digital control circuit can be implemented hardware or software.

Abstract: A communication loop using a subscriber line interface circuit (SLIC) is modified such that it can operate in unbalanced ringing environments as well as balanced ringing environments. This is accomplished by grounding the tip lead of a telephone instrument and creating an open circuit at the tip lead of the SLIC. The ring lead of the telephone instrument and the ring lead of the SLIC are electrically connected, and an AC voltage applied to the ring lead by the SLIC is increased. A power supply is connected to the SLIC and biased to provide the increased AC voltage on the SLIC ring lead while the average voltage on the SLIC tip lead is maintained substantially at ground. The result of this circuitry is a trapezoidal signal meeting the amplitude, loading and crest factor requirements of Bellcore Technical Requirement Publications TA-NWT-000909 and TR-NWT-000057.

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

Abstract: A circuit arrangement for generating charge pulses during digital telecommunications is indicated, whereby subscribers (Tln) of a telephone network are connected by cables with an exchange. The subscriber telephones are connected by electric service lines to an interface unit that is connected to the exchange. The interface unit has a digital interface on the exchange side and at least one analog interface on the subscriber side. A generating circuit (3) is located in the interface unit and produces charge pulses as a function of signals transmitted by the exchange, the charge pulses being transmitted to the respective subscriber (Tln). When loop current flows through the electric circuit of each subscriber (Tln) telephone, the interface unit measures an input voltage that is proportional to the length of the service line. The thus gained voltage value is used to adjust the voltage level of the charge pulses produced by the generating circuit (3).

Abstract: A transformerless battery feed circuit for a digital telecommunications line (100) presents a high impedance to digital signals and a low impedance to direct current, and provides a constant-voltage feed with current limiting. The battery feed circuit comprises a pair of transformerless controlled current sources, one for each lead (T,R) of the line, each taking the form of a high-gain transistor (Q1, Q2) having a collector coupled to a source of power (e.g., a battery V1), a base resistively coupled to the power source and capacitively coupled to its corresponding lead, and an emitter coupled to its corresponding lead. The battery feed circuit further comprises a pair of control circuits, one for each current source, each taking the form of a transistor (Q3, Q4) having a collector coupled to the base of the corresponding high-gain transistor, a base resistively coupled to the emitter of the corresponding high-gain transistor and to the power source, and an emitter coupled to the corresponding lead.

Abstract: A line circuit provides BORSCHT functions and supplies the customer loop through a feed resistor network and current limiter either from a high voltage battery to provide for maximum signaling range or from a lower voltage battery to conserve power. The current limiter operates under the control of a microprocessor/DSP which selectively applies or denies power to isolate or include components for testing and controls the switching in and out of transistors to control the scaling factor between the channel width-to-length ratios of the current mirror's input and output FET transistors according to the type of test or operating condition dictated by the microprocessor while the input reference current to the current mirror is maintained constant.

Abstract: A telephone ringing signal generator includes a DC converter for producing high positive and negative voltages that define peak amplitudes of the ringing signal, which is produced by low pass filtering a generally trapezoidal waveform having these peak amplitudes. The generally trapezoidal waveform is produced by a level-shifting integrator at a frequency determined by a low voltage square wave supplied to the integrator. The integrator comprises a capacitor coupled between a virtual ground point and an output of the integrator and arranged to be charged with two opposite polarities in response to opposite transitions of the square wave, and a resistor via which the square wave is supplied to the virtual ground point. Buffers are provided for buffering the trapezoidal waveform supplied to, and the ringing signal produced by, the low pass filter.

Abstract: A method for reducing frequency-related power losses in a telecommunication line interface circuit comprises operating a switching converter circuit at an optimum frequency. Determination of the optimum frequency is based upon a subscriber loop length. Particularly, the subscriber loop voltage is detected at a battery feed circuit of the line interface circuit, and used to access an optimum frequency stored in an initialized database. The optimum frequency information is received in the switching converter circuit, and determines its operating frequency.

Abstract: A system for providing backup power for a communications system is disclosed. The backup power system of the present invention includes a device for supplying capacitively stored power and a device for monitoring a power level in the communications system. When the monitoring device detects that the power level in the telecommunications system has decreased below a predetermined level, the monitoring device directs the device for supplying capacitively stored power to deliver power to the communications system such that no interruption in power is experienced by the system.

Abstract: A line interface circuit (LIC) used in telecommunications networks operates in either a high frequency mode or a low frequency mode, depending upon the status of its associated customer premises equipment. A LIC main controller detects a change in state of customer premises equipment via a battery feed circuit. If the customer premises equipment is off-hook, a switch associated with a resistor-capacitor (RC) circuit is activated to lower the resistance value of the RC circuit, and thereby, increase the operating frequency of the LIC. During on-hook intervals, the main controller deactivates the switch, and the LIC operates at a lower, default frequency.

Abstract: A communications interface having an isolation circuit for signals from a plain old telephone set (POTS) device to communications electronics. The communications interface having an isolated power supply. The isolated power supply including a flyback transformer for a current loop supply and an isolated power source The telephone line isolation circuit having an optically isolated off-hook detection circuit and an isolation transformer for isolating communication electronics from the telephone current loop. The telephone line isolation circuit providing a ringing circuit for ringing a current loop device, such as a standard plain old telephone system (POTS) device.

Abstract: A hybrid circuit for an electric operating and scanning interface is especially applicable to electronic recorders of electromechanical telephone stations. The hybrid circuit controls voltage and current parameters on different elements of the station in different situations. The hybrid circuit scans the condition of telephone station elements controlled by it, and programmably applies and receives current and voltage to and from the telephone station elements on which it acts.

Abstract: A data access arrangement (DAA) interface for alternately coupling a telephone set to a modem for operation in conjunction with and independent of the central office power supply line. The DAA interface provides an enhanced power supply to supply adequate power to the telephone set when the telephone set, or a computer coupled thereto, communicates with the modem independent of the central office line. Multiple relays are coordinated and controlled via an application program in communication with the modem which detects certain conditions representing incoming and outgoing telephone and data/facsimile calls, and commands the relays to respond to the conditions.

Abstract: The invention provides a method for detecting a call progress tone on a pair of telephone conductors (the telephone line). The level of energy stored in an energy storage device is continually checked. When the level of energy of the energy storage device is below a threshold, the system couples the telephone line to an off-hook impedance. While coupled to the telephone line, the system charges the energy storage device using current drawn from the telephone line, and the system detects the presence of the call progress tone on the telephone line.

Abstract: Disclosed is a network interface unit which comprises a multilayer modular design. The upper layer includes an array of customer bridges. The lower layer includes a splice chamber and a protector panel. The splice chamber includes openings which permit a plurality of units to be stacked. The upper layer is removably mounted to the lower layer so it can be used with existing building entrance protectors which have no interface section.