The circuit selected is from the 1960 Mullard transistor reference manual. The circuit is powered by a single 1.3 V battery and the transistors are germanium.
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...