| ACD | Automatic Call Distribution |
| ASR | Automatic Speech Recognition - stt |
| call leg | inbound or outbound connection between pbx & external party |
| channel | = call leg |
| CNG | Comfort Noise Generation |
| CSP | communications service provider |
| df | Digits Dialed filter |
| ENMS | Electronic Number Mapping System |
| esl | event socket layer |
| gateway | 电话网关、类似 asterisk 的 trunk |
| IMT | Inter-Machine Trunk |
| NAPTR record | NamingAuthority PoinTer Resource Record |
| PBXs | private branch exchanges |
| PTTs | postal, telegraph & telephone services |
| SLA/SCA | Shared Line/Connection Appearance |
| SPIT | Spam over Internet Telephony |
| STT | speech to text |
| TSP | telecommunications service provider |
| VAD | Voice Activity Detection |
| WMI | Message Waiting Indicator |