This circuit recognizes a tone determined by the tuned input circuit (R3 / R4 / C2). The circuit was found in Radio Electronics from the 90s. The 4046 is not a common component today.
This interesting circuit was found in a 1967 Japanese documentation. Transistors are types of...
This assembly circuit using a small motor as a generator was found in Radio Electroics magazine from...
This circuit is of great use today, when solar energy is becoming increasingly important. The...