RCA connectors, also known as phono connectors, are a common type of connector used with consumer-level audio and video systems.
The design is a simple non-locking male/female connection. The male plug has a centre pin surrounded by a ring, the female socket has a corresponding hole for the pin and slightly smaller surrounding ring. The connection is made by simply pushing the plug into the socket.
The most common colour convention is:
Red: Audio, right channel
White or black: Audio, left channel
Some RCA cables are sold with different colour-coding, e.g. black and white audio cables. This is confusing — it's better to stick to yellow, red and white if you can.
A common problem with RCA connectors is that the male centre pin can easily touch the female shield ring when making the connection. Also, being a non-locking connector, the connection can fall apart which sometimes causes the centre pin to stay in contact with the ring or other objects. This results in a nasty hum or buzz.
Because RCA connectors are made for the lower end of the market, they are often made cheaply. Cheap RCA connectors often don't fit well or have poor contact points.
Another disadvantage of RCA cables is that each cable can only carry one signal. In the modern age this is very limiting, given that a simple video/audio signal is made up of at least three signals (video, left and right). SCART connectors are an attempt to address this problem and have become popular in Europe.
RCA is an acronym for the Radio Corporation of America, which introduced the design for this type of connector in the 1940s.
Phono is short for phonograph, and is so named because this connector was originally used to connect the output of a phonograph to an amplifier.