Commercial CW Burst test set, Racal-Decca, c.1980.

Because of the wide bandwidth needed, the use of coaxial telephone cables for digital transmission has led to the need for more stringent testing techniques. It is important to measure a condition known as impedance regularity when cables are put to such use. Continuous wave (CW) burst is an improvement over earlier testing techniques as echoes from unwanted components can be rejected by selecting a suitable time delay and duration of the burst of CW. The acquisition of this Racal-Decca test set is an important element in representing the transition from analogue to digital signals.