Found in a 1980s telecommunications documentation, the circuit presented acts as a product detector. The modulator or mixer in the square may be that of the previous circuit.
The critical components for this 1970s project are transformers. The original transistors are made...
Found in a 90s Popular Electronics, this circuit keeps an LED on when a phone is in use. Can be...
We found this frequency meter circuit in a 1974 documentation. The circuit is powered by 12 V and...