| Abbreviation | Definition |
|---|---|
| SSP | Secure Service Provider |
| SSP | Service Switching Point |
| SSRC | Synchronization SouRCe |
| SSU | Synchronization Supply Unit |
| STAN | Supply of Telstra Account Number |
| STAP | Specialized Telecommunication Assistance Program |
| STBS | Sysnet Telecom Billing System |
| STC | Signaling Transport Converter |
| STCD | Struttura Tecnica del Commissario Delegato |
| STD | Secondary Telecom District |
| STD | Subscriber Trunk Dialing |
| STD | Subscriber Trunk Dialling |
| STDM | Statistical Time Division Multiplexer |
| STE | Section Terminating Equipment |
| STE | Syrian Telecommunications Establishment |
| STI | Speech Transmission Index |
| STK | Satellite Tool Kit |
| STMB | Space-Time Multiple Beam |
| STN | Satellite Telecommunications Networks |
| STND | Statewide Telecommunications and Network Division |