This timer, like the previous circuits, uses a currently uncommon integrated circuit. The time is given by capacitor C1 and R2 which has the range of values indicated in the diagram.
This PWM control circuit was found in an old documentation, but appears elsewhere on this site...
Based on TTL logic this circuit can vary both the frequency and the pulse width of a rectangular signal....
The critical components of this project from a 1978 publication are the transformers, which can be...