| Abbreviation | Definition |
|---|---|
| TWS | Two-Way Simultaneous |
| TX | Transfer |
| TX | Transmit |
| TXC | Transmission Control |
| TXD | Transmit Data |
| TXE | Transmission Experiment |
| TXL | Traffic Exchange Launcher |
| TXP | Transmission Problem |
| TXTHU | Text Hook-Up |
| UA | Unique Address |
| UA | Unnumbered Acknowledge |
| UAA | Universally Administered Address |
| UAC | User Agent Client |
| UAG | Unified Access Gateway |
| UAM | User to Address Mapper |
| UAT | UnAvaliable Type |
| UBP | Upward Bidding Protocol |
| UBR | Universal Broadband Router |
| UBR | Unspecified Bit Rate |
| UBU | Unicode Big Unmarked |