The configuration shown was found in an old Poptronics but can be easily assembled using a common calculator photocell. The relay is according to the supply voltage.
This circuit was suggested by Texas Instruments in a manual of operational amplifiers. Other...
Found in American documentation from the 1980s, this circuit shows how to use an LM3909 pulsator in a...
This circuit was found in an Elektor from the 90s. The integrated circuits are not very common...