mini-phone connector - technical definition

Also called an "eighth-inch connector" or "3.5 mm connector," it is a plug and socket widely used for all variety of audio and video connections on portable devices. For example, mini jacks are the headphones sockets on digital music players and portable DVD players. Sub-mini jacks, a smaller 2.5 mm version, are widely used for the headphones on many cellphones and other compact devices.

Mono and Stereo
Mini and sub-mini connectors come in two-wire mono and three-wire stereo. You can tell the difference by the number of separated elements at the end of the plug. A four-conductor variety is also used (see tip and ring). See phone connector, RCA connector, A/V ports and plugs & sockets.