A new double pulse system has been designed and tested which offers several advantages over previous methods of generating and delaying one squarewave pulse with respect to another. Characteristics of the new system are, fast rise and fall times (2 nanoseconds typical); high power pulses (150 V into 50 ohms); very low time jitter (less than 0.2% of pulse separation time); accurate repeatability of time delay plus or minus 1% typical); extremely wide range of time delay (nanoseconds to milliseconds); d.c. readout of the time separation of the two pulses accurate to plus or minus 1% and suitable for x-y pen recorders. A special summing junction circuit allows both pulses to be applied to the same load without power being split between the load and the other pulse generator, and also without the first pulse prematurely triggering the second pulse or affecting its amplitude. Some results obtained by applying this system to the study of electron-hole plasma decay are briefly presented. (Author).