Why are glow lamps useful as pilot lamps and indicator lamps?

Glow lamps are highly effective as pilot and indicator lamps due to several key operational characteristics:

• Energy Efficiency: They consume very little power, making them ideal for applications that require continuous operation.1
• Longevity: These lamps are designed to last for a long time, reducing the need for frequent maintenance or replacement.1
• Operational Stability: Because the glow discharge tends to maintain a constant voltage across the lamp, they are reliable for signaling purposes and can even function as a voltage regulator in certain circuits.1

A glow lamp functions by applying a voltage difference between plates within a small bulb, which causes an enclosed gas—typically neon or argon—to emit a faint light. This mechanism, where light is produced by the glow of gas near the cathode, distinguishes it from traditional filament-based lighting.12