RJ48C and RJ48S RJ48X 8 position jack pin out for T1 termination and local area data channels/subrate digital services

RJ48C

UNIVERSAL SERVICE ORDER CODE (USOC): RJ48C

Mechanical Arrangement: Miniature 8-position jack. Typical Usage: 1.544 Mbps digital services.
Electical Network Connection: T&R, T1 R1, conductors 7 and 8 provide cable shield integrity.
Conductors 3 and 6 are reserved for future use.

RJ48S
DDS Telco on RJ45

UNIVERSAL SERVICE ORDER CODE (USOC): RJ48S

Mechanical Arrangement: Miniature 8-position keyed jack.
Typical Usage: Local area data channels/subrate digital services.
Electrical Network Connection: One or two line T&R or T&R, T1.

RJ48X

Understanding USOC and what those RJ codes really mean. The Universal Service Ordering Code (USOC) system was developed by the Bell System and introduced by AT&TO in the 1970s to connect customer premises equipment to the public network. These codes, adopted in part by the FCC, Part 68, Subpart F, Section 68.502, are a series of Registered Jack (RJ) wiring configurations for telephone jacks that remain in use today.