Phone Jack Types

Written by lesley graybeal
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Phone Jack Types
(Andy Sotiriou/Photodisc/Getty Images)

Different types of phone jacks can be found in different countries around the world. The most common type of phone jack is the RJ11 jack used in the United States, as well as some other countries in North America, Central America, Asia and Europe. The letters “RJ” stand for “registered jack,” and many other phone jack types use slightly different registered jacks to accomplish different telecommunications purposes.

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While all American phone jack types begin with the letters “RJ,” they may end with one of several suffix letters indicating the type of wiring or mounting used with that registered jack. The letter “C” indicates that the jack is flush mounted, while “W” indicates that it is wall mounted. A single-line jack uses the letter “S” and a multiple-line jack uses the letter “M.” The letter “X” denotes a complex multi-line jack connected in a series.


RJ11C and RJ11W are the two most common phone jack types in the United States, and both are used to connect a telephone, modem or other ancillary device to a modular telephone line. A modular telephone line means that the phone line can be plugged into a jack, rather than feeding from the phone directly into the wall.


These phone jack types indicate use with single-line, non-key phones that need to be connected to a key system. RJ14 phone jacks are similar to RJ12 and RJ13, except that they connect two-line, non-key phones to a key system, rather than single-line, non-key phones.


RJ15W and RJ15C phone jacks are weatherproof jacks. This type of registered jack is used for communications lines in marinas and on board boats, as well as any other location in which phone jacks may be exposed to water and extreme weather conditions.


RJ17 jacks are phone jacks used with hospital equipment connected on a closed circuit, and allow hospital equipment to transmit data to other devices.


RJ21X phone jacks use a complex multi-line configuration that is most commonly used with traffic data recording equipment.


RJ24X jacks are the type of registered jack most commonly used for phone line systems that communicate with conference devices or play music on hold.

RJ31 and RJ32

The RJ31X and RJ32X are complex series communication systems used for automatic dialers, alarm warning systems and alarm reporting devices that dial automatically to transmit information.


The phone-jack types with numbers RJ41-RJ48 are used to configure different types of networks for using modems and other programmed data devices to communicate within a local area.

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