The venerable RCA plug gets its name from the RCA Corporation, which popularized its use on radios and phonograph players as far back as the 1940s. The RCA connector is a round plug with a central tip and a metal ring, separated by insulating material. The tip has a smooth, domed shape. The shape and design makes the connector extremely easy to plug and unplug into equipment. RCA connectors are often used with coaxial cables, where the center conductor terminates to the tip, and the coaxial shield is in contact with the metal ring of the plug. Even though they are used for video applications, most RCA connectors do a poor job of maintaining a precise impedance. As such, they are rarely used for broadcast or professional applications. The RCA plug is sometimes referred to as a Cinch or phono connector. RCA interfaces are very common on consumer electronics devices, for applications such as composite video, component video, line-level audio, and S/PDIF digital audio.