Other settings like this can be found on this website. This makes use of old operational amplifiers, as the publication where we obtained, but equivalents can be used.
This configuration, which produces a rectangular signal compatible with CMOS and TTL logic, was...
We found this circuit in a 1977 Radio Shack brochure. Transistors can be the most modern BC548 for NPN...
The basic idea of this circuit is to convert the indication of a magnetic sensor to an audio tone...