8 pin RJ48 (8P8C) male connector at the cable.
8 pin RJ48 (8P8C) female connector at the device or outlet.
The RJ-48 is a registered-jack wiring of the 8-position (8P8C) modular connector used for digital carrier circuits — most commonly a T1 line (1.544 Mbit/s) or fractional T1, and also 56K and T3 services. A CSU/DSU (Channel Service Unit / Data Service Unit) terminates the carrier’s digital circuit and connects it to customer equipment such as a router or bridge.
Although it looks like an ordinary RJ-45, the RJ-48 differs in its pin assignment, voltage levels and line capacitance, and it is wired with shielded twisted pair (STP) rather than the usual unshielded twisted pair (UTP). The RJ-48X variant adds shorting bars that loop the line back automatically when the plug is removed.
| Pin | Signal | Description |
|---|---|---|
| 1 | R1 | transmit ring to network |
| 2 | T1 | transmit tip to network |
| 3 | not used | |
| 4 | not used | |
| 5 | not used | |
| 6 | not used | |
| 7 | T | receive ring from network |
| 8 | R | receive tip from network |
RJ-48C Jack Connector pinout
| Pin | Signal | Description |
|---|---|---|
| 1 | R1 | transmit ring to network |
| 2 | T1 | transmit tip to network |
| 3 | not used | |
| 4 | T | receive tip from network |
| 5 | R | receive ring from network |
| 6 | not used | |
| 7 | not used | |
| 8 | not used |
Notes
- The RJ-48C jack (second table above) is the standard T1 assignment: pins 1 & 2 and pins 4 & 5 carry the two signal pairs, pins 3 & 6 are reserved, and pins 7 & 8 are the cable shield.