Abstract: An embodiment of the present invention is a power generator which provides a power waveform for applying power to ringing circuits and message-waiting lamps (Ring/MWL) in standard analog telephones in a PBX and which power generator reduces power dissipation. In particular, an embodiment of the inventive power generator includes: (a) a controller which generates a low-level signal representing the power waveform and a timing and control signal indicative of various portions of the low-level analog signal; (b) a circuit, responsive to the timing and control signal, which alters the output of a power supply; and (c) a power amplifier, responsive to the low-level signal and the output of the power supply, which amplifies the low-level signal to produce the power waveform.

Abstract: A method and apparatus for determining whether a telephony system malfunction is caused by defective telephone company trunk lines connected thereto, or caused by defective system equipment. The present invention comprises two double pole double throw relays having connections arranged whereby a pair of telephony equipment interface channels have multiple remote testing capabilities. The present invention performs trunk rolling and/or inter-channel loop back testing under local or remote control.

Abstract: A distortion measurement system for measuring distortion as low as 0.002% includes an ultra low distortion oscillator having a relatively fast response which is achieved by switching the time constant of the control loops of the oscillator during settling. The analyzer section included in the distortion system has a unique notch filter which provides low distortion. This is achieved by adding together two 90.degree. all pass phase shifters. In addition, automatic tuning is provided by two feedback control loops; one is responsive to out-of-phase signals which controls the RC filter circuits of the phase shifters and the other responds to the in-phase signals which controls the output summing junction of the notch filter. Finally, a feedforward type of simultaneous tuning is accomplished by ganging the oscillator frequency adjustment with the analyzer.

Abstract: A distortion measurement system for measuring distortion as low as .002% includes an ultra low distortion oscillator having a relatively fast response which is achieved by switching the time constant of the control loops of the oscillator during settling. The analyzer section included in the distortion system has a unique notch filter which provides low distortion. This is achieved by adding together two 90.degree. all pass phase shifters. In addition, automatic tuning is provided by two feedback control loops; one is responsive to out-of-phase signals which controls the RC filter circuits of the phase shifters and the other responds to the in-phase signals which controls the output summing junction of the notch filter. Finally, a feedforward type of simultaneous tuning is accomplished by ganging the oscillator frequency adjustment with the analyzer.

Abstract: A distortion measurement system for measuring distortion as low as 0.002% includes an ultra low distortion oscillator having a relatively fast response which is achieved by switching the time constant of the control loops of the oscillator during settling. The analyzer section included in the distortion system has a unique notch filter which provides low distortion. This is achieved by adding together two 90.degree. all pass phase shifters. In addition, automatic tuning is provided by two feedback control loops; one is responsive to out-of-phase signals which controls the RC filter circuits of the phase shifters and the other responds to the in-phase signals which controls the output summing junction of the notch filter. Finally, a feedforward type of simultaneous tuning is accomplished by ganging the oscillator frequency adjustment with the analyzer.