The Tektronix 108 is a 1 ns rise-time pulse generator intended for calibration of the 517.
It is the predecessor of the more complex and faster 109. Repetition rate of the 108 is 240 Hz and the maximum pulse amplitude is 10 Vp into a 50 Ω load. It uses a mercury switch and selenium rectifiers. The output is through an N connector.
The price in July 1959 was $125.
Referring to the output network photo below, current flows in from the left through the 1 kΩ resistor and charges the four red 0.1 μF capacitors in parallel. When the mercury switch (terminals visible at lower right) closes, the capacitors are suddenly connected to the output load of the pulse generator, causing a sharp step in the output voltage. The starting voltage of the step is typically 0 V. The final voltage is adjustable, both in polarity and magnitude. The range is approximately -10 V to 10 V.
- Tek 108 right.jpg ight view, selenium recitifier