This circuit was found in a 80s American documentation. The zener diodes determine the points of action of each stage and the transistors can be general purpose types.
With the configuration shown in the figure, a common 12 V lamp lights up when light no longer...
This circuit was obtained in documentation on medical applications from 1966. The circuit is used in...
We found this circuit in an Australian publication from 1991. The circuit has good sensitivity, presenting...