A neon sign is a very simple device. It consists of a vacuum-tight glass tube, fitted at each end with an electrode. Inside the tube is a small amount of rare gas. Connected to the two electrodes is a source of high-voltage electrical power. When the current is turned on, the tube glows with a steady piercing light.

Neon signs offer a variety of colours, from pastels to deep, rich shades. The neon look is very distinctive and highly visible at night.