USOC 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.

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