Abstract: Digital amplifying circuitry delays a digital data signal (INR) to produce an output signal (VoutR). The delayed digital data signal is converted to an analog signal (VinR) for amplifying by an amplifier (10R). Signal amplitude information (S_R[n]) contained in the incoming digital data signal is detected during the delaying. The signal amplitude information is converted to a first control signal (S_Io_NEG[n]) in response to which an adjustable maximum available supply current of the amplifier is produced of least sufficient magnitude to avoid distortion during the amplifying to produce the output signal. The signal amplitude information also is converted to a second control signal (S_AMPLITUDE[n]) in response to which a supply voltage (VNEG) of the amplifier is controlled.

Abstract: Digital amplifying circuitry delays a digital data signal (INR) to produce an output signal (VoutR). The delayed digital data signal is converted to an analog signal (VinR) for amplifying by an amplifier (10R). Signal amplitude information (S_R[n]) contained in the incoming digital data signal is detected during the delaying. The signal amplitude information is converted to a first control signal (S_Io_NEG[n]) in response to which an adjustable maximum available supply current of the amplifier is produced of least sufficient magnitude to avoid distortion during the amplifying to produce the output signal. The signal amplitude information also is converted to a second control signal (S_AMPLITUDE[n]) in response to which a supply voltage (VNEG) of the amplifier is controlled.

Abstract: A network interface circuit that screens out transient signals and provides an indication to the line side that an actual event has occurred, so that appropriate discrimination circuitry is powered up to determine the exact nature of the actual event only when actually needed. The present invention develops an AC signal that represents the events that are desired to be detected. This AC signal is timed so that it has a sustained rate (e.g., a 1 millisecond burst) that is unlike any transient that would occur on the line. Thus, unless the incoming signal meets the timing requirements of the circuit, it is disregarded as a being a transient and no action is taken to determine the exact nature of the signal. This avoids the need to invoke the discrimination circuits that have large power requirements until they are actually needed.

Abstract: Disclosed is a method and apparatus which facilitates the use of existing power that is ordinarily unused or discarded to provide power to a telephone interface circuit when the circuit is in the on-hook state, thereby alleviating the need to use loop current to power the interface during the on-hook state. Existing clock signals are used to charge capacitors that are normally used for capacitive coupling of digital data across the high voltage isolation barrier. Although only small-value capacitors are needed for transmitting data across the capacitive interface, larger-value capacitors are used and are configured to form a charge pump to generate power to the interface at all times. Thus the interface always has a steady source of power available for use, including during the on-hook state for powering circuitry that can detect, modulate, and transmit on-hook signals across the capacitive interface.

Abstract: A telephone line interface circuit with event detection capabilities is provided that screens out transient signals and provides an indication to the line side that an actual event has occurred; so that appropriate discrimination circuitry is powered up to determine the exact nature of the actual event only when needed. An event detector develops an AC signal that represents the events to be detected. This AC signal is timed to determine its sustained rate. The sustained rate has a timing threshold which is higher than a transient that occurs on the line. If the incoming signal does not meet the required threshold timing, it is disregarded as being transient and no action is taken. If the incoming signal meets the threshold requirement, the line interface circuit switches to the full power mode and facilitates the actual data transmission.

Abstract: The present invention provides a digital pre-distortion filter in arrangement with a data access arrangement (DAA) on the component side (e.g., in a modem chipset). This arrangement of the pre-distortion filter outside of the DAA allows digital processes such as digital emulation of the central office impedance to remain unaffected by the pre-distortion in the transmitted signal, allowing the dynamic range of the transmitted signal to be flattened to minimize return loss without complicating the transfer function of the digital emulation of the central office complex load. In the case of a digital emulation filter, placement of a digital pre-distortion filter outside of an analog-to-digital (A/D) digital-to-analog (D/A) loop also minimizes the noise otherwise associated with the use of a pre-distortion filter. Thus, benefits of a pre-distortion filter can be gained without interfering with emulation of impedance, and without causing a significant amount of noise in the transmitted signal.

Abstract: An AC impedance matching architecture which provides programmable AC impedance matching in a given range using a digital filter to filter a signal fed back from the impedance matched line to generate an AC impedance emulation control signal. The AC impedance emulation control signal is combined with a transmit signal (if desired) and drives a voltage controlled current source, which is in parallel with a reference impedance. A voltage is developed across the reference impedance to drive, e.g., the telephone line. The reference impedance is chosen based on a desired maximum AC impedance. The gain of the digital filter, a first order sigma delta filter in the disclosed embodiment, is chosen based on the desired value of the AC impedance. The transfer function of the digital filter is derived based on a desired AC impedance.

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 solid state circuit breaker which provides high voltage isolation between a control circuit and a power source is described. The circuit breaker comprises a receiver for providing a control signal in response to a transmitter that is electrically isolated from the receiver, a solid state switch that closes in response to the control signal thereby allowing a load current to flow through the switch, a current sensor for measuring the load current, and an inhibit circuit responsive to the current sensor for inhibiting the control signal when the load current exceeds a predetermined magnitude thereby opening the switch without adjusting the transmitter. After opening the switch, the inhibit circuit is responsive to the transmitter for allowing the control signal thereby closing the switch.

Abstract: A fast turn-off circuit for solid-state relays or the like. The relay has a photodiode array for controlling the conductivity of an output transistor. A JFET switch closes to discharge the gate of the output transistor when a photodiode array stops producing current. A bipolar transistor switch, upon detecting the JFET switch closure, discharges the photodiode array.