Registered Jack

Registered jacks (RJ) were introduced by the Bell System under a 1976 FCC order ending the use of protective couplers provided exclusively by the company and allowing CPE to be connected directly to the PSTN. CPE still had to be registered with the company and customers needed to order the appropriate “registered jack” in accordance with the Universal Service Ordering Code (USOC) specified for each configuration.

Each Registered Jack USOC specifies the connector used and the function of each pin on that connector. The code is comprised of the letters RJ followed by a number or letter-number combination, and one or more of the following suffixes:

  • C: flush-mount or surface mount
  • F: flex-mount
  • W: wall-mount
  • L: lamp-mount
  • S: single-line
  • M: multi-line
  • X: complex jack

The RJ codes were adapted by the FCC and codified in the Code of Federal Regulations (CFR), Title 47 CFR Part 68, Subpart F which governed the direct connection of Terminal Equipment (TE) to the Public Switched Telephone Network (PSTN) in the United States. The code became law in 1980.

ANSI/TIA-968-A, “Technical Requirements for Connection of Terminal Equipment to the Telephone Network” is the current standard. It incorporates the standard T1.TR5-1999, “Network and Customer Installation Interface Connector Wiring Configuration Catalog” and supersedes FCC Part 68.

Very few of the original RJ codes survive to present day except those using 6-pole modular connectors, such as RJ11 and RJ13.

Modular connectors are often used for non-telephone applications such as Ethernet but are entirely out of the scope of FCC/TIA regulations are the use of RJ designation is incorrect. For the correct terminology, refer to the ANSI/TIA-568-D standard.

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Created 2022-02-09 01:38 by Stephen B (Revised 2023-03-10 01:18)

Keywords: ANSI/TIA-968-A, Registered Jack, Registered Jacks, RJ, and TIA-968-A

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