This is a simple bistable multivibrator... Using 1 PNP and 1 NPN Transistor... Switch 1 triggers the LED on & switch 2 triggers it off... This is actually an SCR or thyristor... Thyristor is PNPN semiconductor device... They are useful but rare... So you can easily make one using two very common Transistors... (diagram of SCR: right side... Logic sources have been used to indicate 3 terminals of an SCR)
