This circuit uses a feedback integrator. We found it in Ferranti's transistor manual from 1974. Transistors are general-purpose types at the time.
This circuit generates trains of pulses in regular intervals determined by R1 and C1. The...
The first transistor can be the BF494 and the other BC548 on this MW radio found in a...
We found this circuit in a Popular Electronics from 1992. It modulates an infrared LED with a...