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 frequency band below 15 kHz converter was found in a Popular Electronics from the 90's. The...
The circuit presented is a 10 MHz oscillator with crystal, which already has several splitters for...
We found this circuit in the November 1992 issue of Radio Electronics magazine. The circuit has...