It is run off a pair of 22.5 V batteries. A 100 kHz oscillator built with a 2N964 transistor drives a 100 mA, 6 pF tunnel diode. The output signal is delayed by 30 ns through a length of RG-174 cable to allow for pre-triggering.
The 4S2 is supposed to display a rise time of no more than 105 ps using this pulser.
The 4S2 pulser is similar to a slightly later instrument, the 067-0513-00.