... bridge cranes used in harbors,metallurgies,large plants BC-3B Outdoor siren and flashing Light is specially designed for overhead travelling cranes, ... which houses amplifier circuit, siren and super bright LEDs, providing environmental protection, shockproof, ease of mount and operation and external long life.Customized ... not work Quantity/Delivery Day: 50 Sets / 5 Days Outdoor Siren and Flashing Light