We found this circuit in a Hands-On Electronics from the 90s. The circuit must be connected to an external amplifier. Frequency control is capacitive, using an antenna for this purpose
This circuit was found in National Semiconductor documentation from the 90s. The circuit uses two...
This bargraph circuit has already been explored in other versions in articles on this site. This is...
We found this circuit in a Popular Electronics of the 80s. The circuit can be made with almost any...