Diver down flag. A diver down flag, or scuba flag, is a flag used on the water to indicate that there is a diver below. Two styles of flag are in use. Internationally, the code flag alfa/alpha, which is white and blue, is used to signal that the vessel has a diver down and other vessels should keep well clear at slow speed.
Familiarize yourself with some friendly network cables and take a closer look at common types of network media, including twisted-pair cable, coaxial cable, fiber-optic cable, and wireless.
Wires & Cables - An Introduction to Wired Communications Media. Media whether its contains wires or it is wireless allows two or more people to communicate with one another without being physically present (William.B & Sawyer.S, 2007. Using Information Technology. The McGraw-Hill Publishing Inc: New York).