This simple logic level tester was found in Radio Electronics from the 90s. The inverters are of the 4009 type and the power comes from the circuit being analyzed.
This 1956 direct amplification radio circuit was found in a documentation from Sylvania that...
This conventional oscillator with the 741 can be precisely adjusted to produce a 400 Hz signal. The...
This circuit uses two diodes in a doubling configuration to receive medium-wave range signals. The...