| Abbreviation | Definition |
|---|---|
| ADTN | Agency Data Telecommunications Network |
| ADTS | Automated Digital Terminal System |
| ADTS-E | Ameritech Digital Transport Service - Enhanced |
| AEE | Agent Execution Environment |
| AF | Assured Forwarding |
| AFPS | Automatic Facility Protection Switching |
| AFRINIC | African Network Information Centre |
| AFSK | Audio Frequency Shift Keying |
| AFTN | Aeronautical Fixed Telecommunication Network |
| AGCH | Access Grant CHannel |
| AGPS | Assisted Global Positioning System |
| AHT | Average Holding Time |
| AIN | Advanced Intelligent Network |
| AIOD | Automatic Identification of Outward Dialing |
| AIP | Administrative Installation Point |
| AIR | Account Information and Refill |
| AIS | Alarm Indication Signal |
| AIS-L | Alarm Indication Signal - Line |
| AIS-P | Alarm Indication Signal - Path |
| AIS-V | Alarm Indication Signal - Virtual |