We found this circuit in a Radio Electronics from December 1963. The circuit combines valves and transistors and has a high input resistance. The circuit is powered by two batteries.
This circuit has a voltage gain of 30 times and passband of 14 MHz. The circuit is from the 1974...
In the figure we have an oscillator circuit by Wien Bridge (Wien Bridge Oscillator). The frequency of...
This timer with 1 second accuracy was obtained in a 1973 documentation. The Buzzer is a low-power type...