What was the 1.5V bulb in the flashlight before? (The kind before LED lamp, the kind of vacuum bulb). such as

Small light bulbs in flashlights (including 1.5V and 3V, 4. 5V) are all low-power incandescent bulbs. Because incandescent lamps have low luminous efficiency, most of the energy is spent on heating, so it is absolutely inevitable that they will be replaced and withdrawn from the historical stage. At present, the component with the highest luminous efficiency is the light emitting diode LED, which also has the characteristics of small size, long service life, vibration and shock resistance, and is not easy to be damaged.