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Modular Jack Wiring

USOC Configurations

Universal Service Ordering Codes (USOC) are a series of Registered Jack (RJ) wiring configurations developed by the Bell System for connection of customer premise equipment to the public network. FCC regulations control the application of these configurations when used for this purpose.

USOC RJ61
USOC RJ61

USOC RJ25
RJ25

USOC RJ14
USOC RJ14 Pinout

USOC RJ11
USOC RJ11 Pinout

USOC RJ31X
USOC RJ31X Pinout

USOC RJ48X
USOC RJ48X Pinout

USOC RJ48S
USOC RJ48S Pinout

USOC RJ45S
USOC RJ45S Pinout

USOC Color Coding

TIA/EIA-568-A Configurations

Two standards were adopted. Both utilize pin/pair assignments that provide superior transmission performance over other 4-pair wiring configurations.

T568A
TIA/EIA T568A Pinout

  • Preferred method
  • Directly compatible with 2-pair voice and Token Ring systems utilizing 6-position connectors.

T568B
TIA/EIA T568B Pinout

  • Optional method
  • AT&T's standard
  • Directly compatible with AT&T phone systems

LAN Configurations

Local Area Network Standards designed to operate over UTP designate pin/pair assignments on modular connectors for signal transmission. While the TIA/EIA configurations (T568A and T568B) support all of these designations, there are some cases where the user chooses to cable only the number of pairs required to support the application.

10BASE-T
(IEEE 802.3)
LAN 10Base-T Pinout
10 Mbps Ethernet over UTP

Token Ring
(IEEE 802.5)
RJ25
4/16 Mbps Token Ring over copper

TP-PMD
(ANSI X3T9.5)
RJ25
100 Mbps FDDI over copper (pending)