This MOSFET circuit for microphone applications was found in the December 1969 issue of Radio Electronics magazine. The transistors are uncommon today.
Using a 4046 PLL this circuit recognizes a 1.6 to 1.8 kHz tone by driving an output LED. The...
This battery charger circuit was found in ancient American documentation. The components are...
This circuit is of great use today, when solar energy is becoming increasingly important. The...