The LM121 integrated circuit is no longer common in our market, with more modern equivalent versions. The circuit is from the 1994 Linear Applications Handbook by National Semiconductor.
We found this interesting circuit in a 1969 American documentation. It shows a solution with...
Here is a high-quality intercom for demanding readers. The circuit is from a 1982 documentation. Of course,...
This circuit can be found on this website in similar versions. The power supply is given in...