This circuit can be adjusted between 0.2 and 2 V to trigger with chosen voltages comparing them with the input voltages. We found it in a 1967 documentation.
We found this circuit with the CMOS4046 in the August 1994 Electronics Now magazine. The circuit is...
This configuration of PWM control with the LM317 was found in a Popular Electronics from the 90s....
This oscillator by Wien bridge is based on stabilization by a small incandescent lamp. The...