This SCR circuit can operate on frequencies from 1 to 20 kHz. We found it in an American documentation from the 60's. The SCR must be according to the load. No information is given about the transformer.
We found this circuit in an English publication from the 1980s. The circuit uses current...
The circuit shown in the figure can be useful in cases where a common telephone extension is used....
We found this circuit in an American documentation from 1977. The circuit must not be powered by a...