Abstract: In one embodiment, the present invention includes a regulator having a pulse width modulation (PWM) controller to generate a PWM control signal based on a voltage level of a load coupled to the regulator, a driver to provide a drive signal to a switching element of the regulator responsive to the PWM control signal, and a power saver coupled between the PWM controller and the driver to receive the PWM control signal and to output the PWM control signal to the driver at a reduced rate during an idle mode of the load.

Abstract: In one embodiment, the present invention includes an apparatus having a current sensor to generate an overcurrent output if a current level of a switched power supply is greater than a predetermined threshold, and a pulse width modulation (PWM) controller coupled to the current sensor. At lower load levels, the PWM controller may disable a drive signal to the switched power supply upon receipt of the overcurrent output, but at high load levels the drive signal is not disabled, even in the presence of the overcurrent condition.

Abstract: In one embodiment, the present invention includes a regulator having a pulse width modulation (PWM) controller to generate a PWM control signal based on a voltage level of a load coupled to the regulator, a driver to provide a drive signal to a switching element of the regulator responsive to the PWM control signal, and a power saver coupled between the PWM controller and the driver to receive the PWM control signal and to output the PWM control signal to the driver at a reduced rate during an idle mode of the load.

Abstract: In one embodiment, the present invention includes an apparatus having a current sensor to generate an overcurrent output if a current level of a switched power supply is greater than a predetermined threshold, and a pulse width modulation (PWM) controller coupled to the current sensor. At lower load levels, the PWM controller may disable a drive signal to the switched power supply upon receipt of the overcurrent output, but at high load levels the drive signal is not disabled, even in the presence of the overcurrent condition.

Abstract: A method and apparatus is provided for impedance matching for an apparatus capable of supporting voice and data. The method includes receiving an input signal having at least one of a voice component, data component, and DC component, and filtering at least a portion of the data component and DC component of the input signal to provide a filtered signal. The method further includes adjusting an input impedance of the apparatus to a first preselected value for the voice band in response to the filtered signal and adjusting the input impedance of the first apparatus from the first preselected value to a second preselected value. The method includes adjusting at least one of a magnitude and phase of the filtered signal to adjust the input impedance to a third value.

Abstract: A method and apparatus are provided for sensing current in a subscriber line. The method includes receiving a current signal from a driver capable of driving the current signal on the subscriber line, and generating a second signal in response to receiving the current signal, wherein the second signal is proportional to the current signal. The method includes receiving at least a portion of the current signal from a driver capable of sinking the portion of the current signal from the subscriber line, and generating a third signal in response to receiving at least the portion of the current signal, wherein the third signal is proportional to the portion of the current signal. The method further includes adding the second signal and the third signal to generate an output signal.

Abstract: A method and apparatus is provided for impedance matching for a system capable of supporting voice and data bands. The method includes receiving an input signal having a voice and data band, filtering at least a portion of the data band of the input signal to provide a filtered signal, and adjusting the impedance of the system for the voice band in response to the filtered signal to provide an output signal.

Abstract: A method and apparatus is provided for impedance matching for an apparatus capable of supporting voice and data. The method includes receiving an input signal having at least one of a voice component, data component, and DC component, and filtering at least a portion of the data component and DC component of the input signal to provide a filtered signal. The method further includes adjusting an input impedance of the apparatus to a first preselected value for the voice band in response to the filtered signal and adjusting the input impedance of the first apparatus from the first preselected value to a second preselected value. The method includes adjusting at least one of a magnitude and phase of the filtered signal to adjust the input impedance to a third value.

Abstract: A sensor capable of being coupled to a transmission line and monitoring a foreign voltage on the transmission line includes a voltage monitoring circuit. The voltage monitoring circuit is adapted to operate in a foreign voltage detection mode in response to receiving a first logic signal and a foreign voltage measurement mode in response to receiving a second logic signal. A method for operating a circuit to detect and measure a foreign voltage on a transmission line includes providing a first logic signal to configure the circuit to detect the foreign voltage. The foreign voltage is detected on the transmission line in the circuit. A second logic signal is provided to configure the circuit to measure the foreign voltage, and the foreign voltage is measured.

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 power cross circuit detects a ring trip condition in order to switch a pair of switch relays to a protection circuit and to appropriate line driver circuitry to enable a talking condition for a telephone. The power cross circuit detects a rise in a DC current across a feed resistor connected to a ring bus and a ring line. The power cross circuit determines a difference in current passing across a first and second sense amplifier connected to respective ends of the feed resistor. The current difference is then converted to a voltage difference, and utilized by the power cross circuit to output a power cross condition when the current difference exceeds a predetermined value.

Abstract: A power cross detection circuit that detects a power cross condition on the ring and tip lines of a telephone system. The power cross detection circuit senses a loop current flowing across a ring feed resistor, as well as a loop voltage at a first node and a second node at opposite ends of the ring feed resistor. Based on these sensed values, a threshold voltage for detecting a power cross condition can be adjusted to detect the power cross condition at a lower voltage value.

Abstract: A power-cross detection circuit includes a zero crossing detection circuit for detecting a first zero crossing of the current from a first positive half-cycle to a first negative half-cycle, a second zero crossing of the current from a second positive half-cycle to a second negative half-cycle, and a third zero crossing of the current from a third positive half-cycle to a third negative half-cycle and a circuit for detecting a voltage level and outputting a first signal when the voltage level exceeds a predetermined voltage level, between the first zero crossing and the second zero crossing and between the second zero crossing and the third zero crossing. The zero crossing detection circuit outputs a second signal based on the first, second and third zero crossings.

Abstract: An apparatus for determining a power cross condition during a ringing state of a telephone. The apparatus also is capable of distinguishing a true power cross condition from a short loop ringing condition, by including a first path for receiving a signal indicative of a voltage across a ring feed resistor exceeding a predetermined value, and determining if that voltage is in an active state for a predetermined amount of time (i.e., 14 milliseconds). The apparatus also includes a second path for receiving a first and second current that flow respectively across a first and second sense resistor connected to opposite ends of the ring feed resistor. On the second path, the first and second currents are subtracted, converted to a digital value, filtered, and compared to a threshold value to determine if a ring trip has occurred. If so, the potential ring trip is sent to a persistence timer circuit, for checking if it is in an active state for a predetermined amount of time (i.e., 104 milliseconds).

Abstract: An apparatus for controlling a supply current to a load, such as a telephone subscriber line, generates an output current responsive to the changes in the load according to a predetermined response profile, which is defined by a plurality of parameters and includes a first range extending from a lower load level to higher load level, and a second range extending above the higher load level. A first control circuit generates a first set of parameters establishing the response profile within the first range; a second control circuit generates a second set of parameters establishing the response profile within the second range; and an apportionate feed circuit apportions signals within the apparatus. The first control circuit receives a load indicating current and first reference current, establishes the lower load level, and cooperates with the apportionate feed circuit to impose a first set of the operational parameters in generating an output current within the first range.

Abstract: A system for the prevention of the theft of televisions sets and other appliances from motels and the like requires the modification of the appliance by connecting a quartz crystal resonator across its terminals. A frequency-modulated oscillator connected to a transmission line linking all of the appliances is employed to stimulate the crystals in sequence. A transmit-receive switch operating at 100 herz frequency and phase detection between the oscillator and the echoes from the crystals improve selectivity, while a counter keeps track of the crystals heard from. An alarm and a visual display of a number indicate the time and place of a theft.