Found in a 90s R-E Experimenter Handbook, this circuit has a greater gain than the previous one for presenting two stages. The integrated circuit used is uncommon today.
We found this circuit in a 1998 documentation. It tests common household appliances to see if they...
This circuit uses a triac to detect the level of a reservoir, and a sensitive SCR connected to the...
We found this circuit in an English publication from 1980. The transistor can be either the BC548...