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.
This circuit with the ULN3784B appeared in the October 1984 issue of Radio Electronics magazine. It can...
The circuit shown in the figure was suggested by National Semiconductor in its 1994 Linear...
The 74123 TTL integrated circuit consists of a monostable that can be configured to generate...