reduce the propagation velocity sufficiently below the speed of light, eliminating radiation loss from a surface wave along the surface of a long straight wire. This modification also had the effect of greatly reducing the footprint of the electromagnetic fields surrounding the wire, addressing the other practical concern. Finally, Goubau invented a method for launching (and receiving) electrical energy from such a transmission line. The patented Goubau line (or "G-line") consists of a single conductor coated with dielectric material. At each end is a wide disk with a hole in the center through which the transmission line passes. The disk may be the base of a cone, with its narrow end connected typically to the shield of coaxial feed line, and the transmission line itself connecting to the center conductor of the coax. Even with the reduced extent of the surrounding fields in Goubau's design, such a device only becomes practical at UHF frequencies and above. With technological development at terahertz frequencies, where metallic losses are yet greater, the use of transmission using surface waves and Goubau lines appears promising. E-Line From 2003 through 2008 patents were filed for a system using Sommerfeld's original bare (uncoated) wire, but employing a launcher similar to that developed by Goubau. It was promoted under the name "E-Line" through 2009. This line is claimed to be completely non-radiating, propagating energy by a previously ignored transverse-magnetic (TM) wave. The intended application is high information rate channels using existing power lines for communications purposes. See also Power line communication Single-wire earth return Surface wave References Power cables Electric power distribution