This circuit is for old telephones with analog lines. It was found in the May 1988 Radio Electronics magazine. The circuit is powered by the line signal voltaje.
The circuit shown is from a 1993 documentation. It uses two FETs in an oscillating configuration that...
This output step with a transistor can be used in experimental radios and intercoms or as a signal...
This circuit, for bands above 15 MHz, was found in an Argentine publication from the 1970s. The L1...