This sound meter or sonometer was found in a Popular Electronics from the 80's. The circuit can be easily implemented today, and the microphone is made of electret or ceramic.
This circuit was found in a 1982 documentation. It uses only one integrated circuit and can be...
Only those who know the secret activation code will be able to turn on the device connected to...
This 2 meter (144 MHz) preamplifier is intended for use with portable transceivers. The...