With this circuit it is possible to obtain a higher voltage from a zener diode. The circuit is from a 1970’s EEE. The device used as a constant current source is uncommon today.
This alarm, from a 1996 magazine, can be fitted with two BC548s in the original configuration...
Using only one general purpose transistor this circuit is powered by batteries. The lamp of the...
Can be used as a shield, this old American documentation circuit offers digitally selected...