English: Picture of antenna feeder line from longwave radio transmitter in Solec Kujawski, Poland. The aerial mast of the station, which broadcasts at 225 kHz with a radiated power of 1200 kilowatts, is visible in the background. This type of transmission line is called a cage line, and is used for high power low frequency transmission lines. It functions similarly to a large coaxial cable. The inner bundle of wires and the outer ring of wires carry equal magnitude and opposite phase RF currents to the antenna. The outer ring of wires is connected to ground and serves as a shield.