Today we can call this circuit a baby monitor. It is a microphone amplifier found in a publication by Hugo Gernsback from 1960.
This well-designed bistable configuration is for educational purposes. We found it in the...
This low power bass booster is from the 1977 National Semiconductor Audio Handbook. The circuit is...
This circuit, well known to our readers, only has a slightly different schematic representation, as it was...