USOC - Universal Service Ordering Codes

The Universal Service Ordering Code (USOC) system was introduced by AT& T in the 1970's as a means of identifying telecommunication services and equipment. Some of these codes were later adopted by the FCC and are now (usually incorrectly) used universally to describe telephone jacks such as RJ11 and RJ45. Our RJ code table provides the description for RJ codes and provides typical examples for each code.

Abbreviation
RJ	Registered Jack	(Prefix)
C	Flush or Surface Mount Jack	(Suffix)
W	Wall Phone Jack	(Suffix)
X	Complex Multi-line or Series type Jack	(Suffix)

R J Number	Specific Installation Application
RJ11C and RJ11W	Single line phones, accessories, answering machines, and modems
RJ14C and RJ14W	Two line phones, accessories and answering machines
RJ21X	1 - 25 single or multiple line circuits bridged to network or customer equip
RJ22	Used for Handsets or Headsets
RJ25C	Three-line-phones and accessories
RJ31X and RJ38X	Burglar and fire alarms circuits
RJ41S and RJ45S	Single line fixed loss loop data installations
RJ48C/J and RJ45S	Four wire data circuits
RJ61X	Four line phones and accessories