| Abbreviation | Definition |
|---|---|
| AT | Access Terminal |
| AT | ATtention command |
| ATA | Analog Telephone Adapter |
| ATB | Above-ground Telecommunications Backbone |
| ATB | All Trunks Busy |
| ATCA | Advanced Telecom Computer Architecture |
| ATCA | Advanced Telecom Computing Architecture |
| ATCA | Advanced Telecomm Computing Architechture |
| ATCI | Android Telephony Command Interface |
| ATII | APAC Telecom Innovation Initiative |
| ATIS | Automatic Transmitter Identification System |
| ATLAS | Accessing Telecoms Links Across Scotland |
| ATM | Asynchronous Transfer Mode |
| ATM | Automated Transmissions Machine |
| ATMT | Anti Theft Mobile Tracker |
| ATN | aeronautical telecommunication network |
| AToM | Any Transport over MPLS (Multi-Protocol Label Switching) |
| ATOS | Automated Telecom Ordering System |
| ATP | Association of Telecom Professionals |
| ATR | Advanced Telecommunications Research |