We found these circuits in a 90s Radio Electronics. In them, we have the way to turn a load on and off using pressure switches. The circuit can be used with other types of direct current load.
This circuit has the intensity of the signals controlled by the light that falls on the sensor....
The purpose of the diode in this oscillator circuit is to limit the amplitude of the output...
We found this ladder-shaped signal generator circuit in Radio Electronics magazine from August 1966....