RJ48
RJ48 is a registered jack. It is used for T1 and ISDN termination and local area data channels/subrate digital services. It uses the 8 position modular connector.
RJ48C is commonly used for T1 lines and uses pins 1, 2, 4 and 5.
RJ48X is a variation of RJ48C that contains shorting blocks in the jack so that a loopback is created for troubleshooting when unplugged by connecting pins 1 and 4, and 2 and 5. Sometimes this is referred to as a "smart jack".
RJ48S is typically used for local area data channels/subrate digital services, and carries one or two lines. It uses a keyed variety of the 8P8C modular connector.
RJ48 connectors are fastened to STP (shielded twisted pair) cables, not the standard UTP (unshielded twisted pair) CAT-(1-5).
| Pin | Pair | Signal | Color |
|---|---|---|---|
| 1 | R | RX Ring | Orange/White |
| 2 | T | RX Tip | White/Orange |
| 3 | reserved | White/Green | |
| 4 | R1 | TX Ring | Blue/White |
| 5 | T1 | TX Tip | White/Blue |
| 6 | reserved | Green/White | |
| 7 | shield | White/Brown | |
| 8 | shield | Brown/White |
Read more about this topic: Registered Jack