This circuit is from a 1969 EEE magazine. The transistors are from that time, but the circuit can be implemented with modern equivalents, such as 2N2646 for Q3.
This circuit was found in a 1983 Electronics Experimenters, but it can be easily assembled, since...
Suggested by Amperex in 1968, this circuit is intended for hearing aids. The integrated circuit...
In applications where there is no danger of any contact with live points in the circuit by the...