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.
September 2016 - It can be purchased from Mouser Electornics the iW1818 of Dialog Semiconductor, a...
September 2017 - The Phoenix Contact Mini 7/8 - inch (7/8 inch) sensors and actuator cables can...
This guitar sustain circuit uses only two transistors and can be powered by a 9V battery. The...