The Type 869-A Pulse Generator is an instrument for producing d-c pulses, of either positive or negative polarity. The length of the pulse may be set to any value between 0.3 and 70 microseconds, and the amplitude is adjustable by means of a panel control. Several output impedances are available, selection being made by a panel switch. A complete synchronizing circuit is provided, to enable the repetition rate to be controlled directly from any a-c source of from 5 to 25 volts, and 20 to ,4000 cycles frequency. A synchronizing signal is available at the panel for controlling the sweep circuit of an oscillograph. The instrument may be operated from any 115- or 230-volt, 50-60 cycle line. It is completely shielded against r-f leakage, and may be used to modulate standara-signal generators with output voltage levels as low as one microvolt.