The principle of twinkling lights

Strings of fairy lights are connected in series. However, the structure of the filament inside the lantern is different from that of ordinary lamps. A thin metal wire coated with copper oxide is connected in parallel below the filament of the lantern.
Once the filament of one lantern is fused, the other lanterns will be extinguished instantly, causing the voltage at both ends of the bulb to reach 220V, which will instantly break down the copper oxide coating of the thin metal wire, allowing the lantern to re-form a path, and then The other bulbs continue to work. This is the reason why some of the lanterns connected in series can continue to work even if some of the filaments are fused.
Some colored lights can flicker because a "bubble" is connected in series in the circuit, which causes the circuit to continuously switch on and off, causing the circuit to turn off and on. The structural feature of the bubble jumper is that the filament consists of two parts. One side is an inverted L-shaped lead, and the other side is a filament with a bimetallic piece at the head. The two are usually in contact.
After power is applied, the filament emits light, causing the bimetallic sheet to bend due to heat. If it moves away from its original position, the circuit will be cut off. After the bimetallic sheet cools, it straightens and connects the circuit again. This is the reason why some decorative lanterns can flash while others do not.