This circuit is from a 1977 Radio Shack manual. The photocell is an LDR and the operational one is a 741. Components with non-standard values can be approximated.
The frequency of this type is oscillator is given by the RC network. Calculations can be found in...
This configuration, which appears in other points of this section and website with small...
This circuit is from the 1960 Mullard transistor manual. The transistors are germanium from the...