This circuit was found in the September 1984 issue of Radio Electronics magazine. The frequency is given by the capacitors. The diodes help in the starting process.
This mechanical reverberator circuit for guitar was found in the February 1970 issue of Radio...
Found in an old English publication this circuit uses a dual gate MOSFET. Coils not specified....
This is the receiver for the previous circuit transmitter. Similarly, no information about the...