We found this circuit in an American documentation from the 80s. In it we have the way to control the amplifier gain by an input voltage.
The figure shows how to implement an OR function with two inputs, using a relay. The relay...
The integrated circuit used in this 1987 project is not very common these days. However, if found...
Found in American documentation from the 1980s, this circuit has a diode feedback. At the exit we...