T1 Smart Jack (Intelligent Network Interface Device) is the demarcation point where the carrier network meets the customer premises equipment, providing loopback testing capability via RJ48C connector.
| Pin | Name | Function | Type |
|---|---|---|---|
| 1 | RX+ | Receive pair positive from carrier | BUS |
| 2 | RX- | Receive pair negative | BUS |
| 3 | NC | Not connected | I/O |
| 4 | TX+ | Transmit pair positive to carrier | BUS |
| 5 | TX- | Transmit pair negative | BUS |
| 6 | NC | Not connected | I/O |
| 7 | NC | Not connected | I/O |
| 8 | NC | Not connected | I/O |