We found this circuit in an Australian publication from 1991. It is a kit of the time with input for a guitar pickup. The range is a few tens of meters.
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...