automatic reserve warning light - gives double protection

gives double protection Warning lights fulfill an undeniably important role in many technical in- stallations. However, even in the best of equipment, these lamps can fail. A glowing filament was never in- tended to have an indefinite lifespan. The circuit here cannot prevent the filament from failing, but it ensures that if the warning lamp cannot light, for whatever reason, a reserve light is automatically switched on. This secondary bulb, moreover, will only light when it is absolutely 12V automatic reserve warning light component count for this circuit is just two transistors and two resistors. The principle of the circuit is very simple: assuming there is a fault in the equipment, lamp La1 lights and a small part of the lamp"s current flows to the base of T1, causing this transistor to conduct. As a result of this the base of T2 is effectively shorted to earth and this transistor cannot conduct. No cur- rent flows through the reserve light (La2) in the collector line of T2, s...