The configuration shown allows to obtain a high voltage gain for FETs. FETs can be BF245 or MPF102. The circuit is from the 1977 National Semiconductor FET Databook.
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...