Abstract: A system for performing broadband differential time domain measurement on a subscriber loop. The system comprises a waveform generator coupled to a sampling head. The sampling head includes positive and negative pulse generators each coupled to one of the lines of the subscriber loop. The subscriber lines are in turn also coupled to two inputs of a differential amplifier, whose output is connected to an oscilloscope or other detector.

Abstract: A method and system for restricting telephone access to a predetermined set of telephone numbers. The method includes comparing the output of a caller ID signal decoder to telephone numbers stored in memory and allowing the telephone call to be completed if there is match between the calling party's number and a number stored in memory. The system consists of connection circuitry to which is connected a caller ID decoder, a number comparator, and an off hook detector. These components interact to restricts calls to only those stored in the number comparator.

Abstract: Methods and apparatuses are provided for determining characteristics of an input optical signal in an optical network. An optical signal monitoring apparatus estimates a minimum time interval between transitions in the input signal, determines a clock signal based on the estimated minimum time interval, and performs a time domain measurement on the input signal based on the determined clock signal. The optical signal monitoring apparatus samples the input signal based on the determined clock signal and determines the characteristics of the input signal.

Abstract: Methods and apparatuses consistent with the present invention recover a clock signal from a variable bit rate data signal by estimating, in the time domain, the bit rate of the data signal, and based on the estimated variable bit rate, determining a center frequency of a narrow-band filter for extracting the clock signal from the data signal. A clock recovery circuit consistent with the present invention extracts a clock signal from a variable bit rate data signal by estimating a minimum time interval between transitions in the data signal, generating a plurality of pulses that correspond respectively to transitions in the data signal, adjusting the duration of each of the pulses based on the estimated minimum time interval and inputting into a narrow-band filter the adjusted pulses, determining a center frequency of the narrow-band filter based on the estimated minimum time interval, and extracting in the narrow-band filter the clock signal from the adjusted pulses.

Abstract: A relatively simple voltage regulator comprises a bandgap reference, an error amplifier and a multi-function current mirror. By utilizing only NPN transistors, a high-performance arrangement characterized by good line regulation is achieved.

Abstract: The laser driver circuit of the invention stabilizes the low operating output power level of a laser (301) modulated by a digital input signal, at a fixed preset value L.sub.o, by automatically adjusting the bias current, I.sub.b, supplied to the laser to compensate for variations in the laser threshold due to temperature changes and aging. The circuit includes a fast photodetector (401) which is responsive to the modulated light output of the laser. The photodetector output is combined (306, 308) with a data sensitive reference signal (i.sub.r) and a preset level setting input signal (i.sub.o) which is equal to .eta. times the desired low operating output power level L.sub.o, where .eta. is the coupling coefficient of the photodetector. Reference signal i.sub.r varies in accordance with the input data between a zero value when the input is ZERO and a value equal to what is estimated to be the photodetector output due to the data modulation when the input is ONE.

Abstract: This invention concerns an electrical mechanical instrument transducer which accurately detects the direction of an externally applied force and more particularly, though by no means exclusively, transducer apparatus that provides an electrical signal commensurate to the direction of force or forces resulting from two-dimensional hydrodynamic flow such as waves, currents and tides. A toroidal resistive element and thin resilient wire electrical contact wiper provide accurate and sensitive, yet rugged and reliable transducer operation.