This wired intercom circuit was found in an English publication from the 80's. The integrated circuit can be replaced by an equivalent, just like the transistor which is a general-purpose type.
The operational amplifier is old. The circuit is from an 80's documentation but can be designed...
This configuration, explored in other applications of this section and website, was found in a 90s...
The sensors can be screens having porous tissue between them. When the water moistens them, the...