This is a unit to gate 1 kHz sinusoidal output from a level audio oscillator to produce a tone burst waveform. Gating is to occur as close as possible to the zero crossings of the oscillator waveform. When of the output is to be at 0 volts. When gated on the output level is to be variable up to a maximum of 5 volts RMS with no DC component present. The output resistance is low, not more than 50 Ohm. The unit should be powered from normal laboratory supplies. Design hint to detect the zero crossings of the sinusoid reasonably accurately operate the level oscillator with a large output. z TA