This circuit decodes a 1800 Hz tone used in communications. The circuit is from an American documentation for radio amateurs of the 80's. Equivalent component can be used.
This circuit was discovered in an English publication in 1979. The circuit can still be assembled with...
This circuit is the digital indicator for the previous circuit and can be used with similar...
This circuit tests crystals up to a few megahertz with ease. The circuit is from a 1977...