| Abbreviation | Definition |
|---|---|
| ACF | Advanced Communications Facility |
| ACFQ | Absence Compensation Fair Queuing |
| ACG | Access Control Gateway |
| ACHT | Average Call Handling Time |
| ACHT | Average Call Holding Time |
| ACIS | Andy Charles Ians System solid modelling geometric engine |
| ACK | ACKnowledgment |
| ACL | Asynchronous Connection-Less |
| ACL | Average Call Length |
| ACLR | Adjacent Channel Leakage Ratio |
| ACM | Address Complete Message |
| ACMA | Atlantic Cable Maintenance Agreement |
| ACNA | Access Customer Name Abbreviation |
| ACO | Additional Call Offering |
| ACOU | Additional Call Offering Unrestricted |
| ACP | Active Connection Property |
| ACR | Abandoned Call Rate |
| ACR | Attenuation Crosstalk Ratio |
| ACS | Accelerated Change Service |
| ACTO | Association of Competitive Telecom Operators |