| Abbreviation | Definition |
|---|---|
| IPS | Instructions Per Second |
| IPT | Internet Protocol Telephony |
| IPTD | Internet Protocol Telephony Design |
| IR | International Roaming |
| IRC | International Record Carrier |
| IRMA | Interactive Remote Messaging Application |
| IRTC | Illinois Rural TeleCommunication |
| IS41 | Interim Standard 41 (Inter-Cellular Network Communication Protocol) |
| ISA | Innovative Slot Allocation |
| ISBX | Internet Satellite Broadcast Exchange |
| ISC | Infrastructure Service Charge |
| ISD | International Subscriber Dialing |
| ISDN | I Still Don't Need |
| ISDN | Integrated Services for Digital Network |
| ISDN | ntegrated Services Digital Network |
| ISDNUP | Integrated Services Digital Network User Part |
| ISDP | Intelligent Shared Dual Path |
| ISI | Inter-Symbol Interference |
| ISM | Instrumentation, Scientific, and Medical |
| ISO | Independent System Operator |