We found this circuit in Ferranti's 1974 transistor manual. The components are from the period. The table gives the value of C1 for different frequency ranges.
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...