107
The Tektronix 107 is a squarewave generator. It was intended to be used for calibration of oscilloscopes. It is designed to provide a clean waveform with fast edges and flat tops. The signal starts with an astable multivibrator composed of both halves of a 6BQ7A dual triode tube. The multivibrator circuit is cathode coupled to a pulse shaping circuit, and then to an output stage made from a single 6AU6 tube with a 50-ohm plate load, providing a controlled 50-ohm output impedance. The 50-ohm plate load keeps the voltage gain of output stage low, and the bandwidth high.
The manual is here:
