The Model 211A Square Wave Generator is a precision wide range instrument particularly suited for use with a fast oscilloscope for video amplifier testing, permitting a rapid examination of amplifier frequency characteristics up to many megacycles. In computer, pulse code, telemetering, and similar applications it offers great convenience as a variable trigger source for switching purposes. In television work it can serve as a bar generator. In high frequency applications it is valuable as a modulator source. It also finds use in testing variety of devices such as attenuators, filters, delay tines and audio systems. The Model 211Ahas been designed with two outputs, one 75-ohm output and one 600-ohm output. The rise time of the signal from the 75 -ohm output is only 20 millimicroseconds, which is sufficiently fast to test the response of video devices out to approximately 20 megacycles or to provide a high speed triggering voltage of variable rate. The peak-to-peak amplitude of the signal across the 75-ohm internal impedance is 7 volts, or 3.5 volts peak to peak into a75-ohm external load. This output level may be adjusted with a 60-db step attenuator in combination with an amplitude control, a particularly desirable arrangement when low output levels are required. The second output from the generator provides 55 volts peak-to-peak from a source impedance of 600 ohms. The rise time of this signal is less than 0.1 microsecond with the output level controlled separately from that of the 75-ohm output. Both outputs are used simultaneously.