This circuit is from an old Popular Electronics, but it can be easily implemented nowadays, even adapted to act as a shield. The circuit has the frequency given by C1 and adjusted in R1.
Found in RCA documentation two years 70, this circuit triggers an incandescent lamp at dusk. The...
Found in Popular Electronics from the 90s, this circuit is based on a PLL567 and employs high-end or...
This circuit was obtained in an English publication of 1977. The operational is of the type with...