This circuit is from 1999 documentation. However, it can still be easily assembled, as all components used are common. The sensors can have their quantity increased, being connected in parallel.
This circuit was found in a 1967 Raytheon manual. The transistors are from the time. Equivalent modern...
This circuit was published in a 1979 magazine, but it can still be easily assembled as the...
The circuit presented generates short pulses. This configuration was found in a publication from...