We found this circuit in the old Mullard transistor reference manual from 1960. The circuit is powered by a single battery and the transistors are germanium common at the time.
We found this circuit in an old American documentation. SCRs can be modern equivalent types. The...
We found this circuit in a 1990 documentation. The operational amplifiers are type 741 and the LED is...
This fast-acting circuit uses a 555. We found it in the November 1992 Radio Electronics magazine. The...