This circuit is from a Radio Electronics from December 1964. The components are from the time and modern equivalents for transistors and diodes can be used.
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...