This circuit allows you to read resistors up to 20 M ohms, converting it into voltage. The circuit is from the 90s. The operational ones used admit modern equivalents.
In the figure we have a bridged circuit for the use of an SCR in a full wave control. The diodes...
This circuit accelerates the tripping of a relay when energized. The circuit uses the CA3018...
The sensors in this alarm are reed-switches. In the diagram we have only one, but several can be...