| Term | Definition |
|---|---|
| ABM | Adaptive Bandwidth Management |
| ABR | Available Bit Rate |
| AC | Alternating Current |
| AC-3 | Audio Codec 3 |
| ACC | Advanced Computer Communications |
| ACD | Automatic Call Distribution |
| ACIA | Asynchronous Communications Interface Adaptor |
| ACK | Acknowledge ( char06 - 06H ) |
| ACM | Audio Compressor Module |
| ACO/LT | Alarm Cut Off / Lamp Test |
| ACP | Adjacent Channel Power |
| ACR | Attenuation to Crosstalk Ratio |
| ACT | Absolute Congestion Threshold |
| ADC | Analogue to Digital Converter |
| ADCCMP | Advanced data Communications Control Procedures (ANSI X3,66) |