This small signal amplifier circuit was found in Motorola's 1969 documentation. The FET and the transistor can be of any type and is battery powered since the consumption is very low.
The note sequence for this circuit is achieved through integrated circuits controlled by the 555....
When a voice signal enters this circuit, the volume of the music being played automatically...
We found this configuration in a Radio Shack documentation from 1977. Here we have the way to...