Generation of sinusoidal waveforms for defined periods - for use in telephone network testing is achieved with simple integrated digital and analogue elements

摘要

The system is for the application of bursts of sinusoidal signals to a transmission system such as a telephone network, at a time defined by a pushbutton control, and for bursts of various fixed durations. Basically, the sinusoidal waveform - of which the generator in not shown, - is squared with a linear amplifier comparator circuit and used as a clock for a logic network consisting of two j-K flip-flops. A transistor circuit is primed by a pushbutton which allows the logic network to monitor the clock pulses, giving an output synchronous with the clock. This output inhibits further input to the logic network for a time dependent on various R-C combinations, any one of which may be switched into circuit to give a different deviation. During this time, too, the original sinusoidal signal is gated through an amplifier to the output. The gated output starts at a sinusoidal cross-over point and stops, after a deviation of between 10 mins. and 10 seconds (as required) on another cross-over point. Signal frequencies of 1 Hz to 100 Hz are typical.