This circuit was found in a Motorola documentation from the 70s. The integrated circuit is from the time, an operational power amplifier according to the controlled motor.
This circuit is from 1957 Raytheon documentation. The phone must be high impedance with 600 ohms...
This passive volume compressor was found in documentation from the 1980s. It needs a good...
We found this circuit in a 1983 English magazine, but it can be easily assembled with the BC548...