We found this circuit in an English publication from the 60's. The transistors are of germanium of the time and the headphones must be high impedance magnetic.
Based on an operational of the time, this Popular Electronics circuit can be designed with any...
In the circuit shown in the figure, when the input voltage rises to 27 V, the TL431 triggers the...
This circuit indicates whether a cable or wire is energized by simply approaching its antenna. The...