A Slow Sweep Time-base

The requirements of a time-base suitable for low and intermediate speeds are discussed with special reference to the use of triggered multiple sweeps. A slow sweep time-base having a fast flyback is described. Sweep durations of from 100 sec. to 10 msec. are available with a flyback duration of 1/1000th part of the scan time. Higher speeds, up to 50 μsec. (20 kc/s), may be obtained but with less favourable flyback ratios. The time-base will self-run or may be initiated externally for single or multiple sweeps. The circuit is direct-coupled throughout, and linear traces of identical velocity and duration are generated irrespective of the nature of the triggering wave. The time-base is unaffected by any trigger pulses which may occur whilst the spot is sweeping. Trace brightening is provided from the ractified output of an r.f. oscillator: if required, this oscillator may also be modulated to give timing markers.