Another familiar connector group are those used for audio-visual applications--RCA and phono. While these can't truly be considered to be of the same family, as the various USB connectors are, we'll consider both of them to be in the same vein.
"Phone" Type Connectors
You'll probably immediately recognize the 1/8" version of this connector as a the plug on the end of a pair of headphones. These connectors actually come in three common sizes: 1/4" (6.35mm), 1/8" (3.5mm), and 2.5mm. ¼" size connectors find a lot of use in the professional audio and music community- most electric guitars and amplifiers have 1/4" tip-sleeve (TS) jacks on them. 1/8" tip-ring-sleeve (TRS) is very common as the connector for headphones or audio output signals on MP3 players or computers. Some cell phones will provide a 2.5mm tip-ring-ring-sleeve (TRRS) jack for connecting to headphones that also include a microphone for hands-free communications. Below are a few audio jacks that SparkFun carries in the catalog.
Audio Cable TRS - 1mCAB-18983
Audio Cable TRRS - 1ftCAB-14163
Audio Cable to Alligator Clips - 2.5mmCAB-17983
Audio Adapter - 3.5 mm to 1/4" StereoCOM-11150
The common availability of these connectors and cables makes them a good candidate for general purpose connectivity applications--for instance, long before USB, Texas Instruments graphing calculators used a 2.5mm TRS connector for a serial programming connector. It should be remembered that tip-sleeve connector types are not designed for carrying power; during insertion, the tip and the sleeve can be momentarily shorted together, which may damage the power supply. The lack of shielding makes them poor candidates for high-speed data, but low speed serial data can be passed through these connectors.
Below are a few audio sockets that SparkFun carries in the catalog.
SparkFun TRRS 3.5mm Jack BreakoutBOB-11570
Audio Jack 3.5mmPRT-08032
Familiar as the home-stereo connector of choice for many decades, the RCA connector was introduced in the 1940s by RCA for home phonographs. It is slowly being supplanted by connections like HDMI in the audio-visual realm, but the ubiquity of the connectors and cables makes it a good candidate for home-built systems. It will be a long time before it is obsolete.
Female RCA connectors are usually found on devices, although it is possible to find extension or conversion cables with female jacks on them. Most RCA connectors are connected to one of four types of signals: component video (PAL or NTSC, depending on where the equipment was sold), composite video, stereo audio, or S/PDIF audio.
Male RCA connectors are usually found on cables.