Using a sensitive crystal or ceramic microphone, this circuit can pick up faint sounds through a wall. The circuit has a good range given the use of an RF amplifier transistor.
This simple charger was found in a 1980s documentation. The transistor may be the TIP42 with a...
This circuit is used to run light bulbs around street signs. Incandescent lamps up to 40 W are...
This high frequency or RF amplifier was found in a 90s Popular Electronics. The circuit can be...