Found in na 1980’s English magazine, this circuit produces a strong modulated tone reproduced on a speaker. The power MOSFET can be of almost any type.
This filter rejects 1 kHz signals, being suggested by the manufacturer of the operational...
The circuit presented was found in a Japanese magazine in 1973. The circuit uses transistors of...
This circuit of a 1978 American publication monitors a telephone line by triggering a relay. The...