RJ-21

Definition

Electronics

  • Abbreviation of registered jack-21. A 50-pin connector used, for instance, for tip and ring conductors for up to 25 telephone lines. Although jack generally refers to the connector into which a plug is inserted, RJ-21 may refer to the jack, plug, or both. Also called RJ-21 connector.
http://www.dictionarycentral.com/definition/rj-21.html