| Abbreviation | Definition |
|---|---|
| SDH | Synchronous Digital Hierarchy |
| SDHLR | Super-Distributed Home Location Register |
| SDK | Service Development Kit |
| SDLC | Systems Development Life Cycle |
| SDM | Service Delivery Management |
| SDMA | Space Division Multiple Access |
| SDN | Software Defined Network |
| SDNB | Secondary DN Call Blocking |
| SDP | Service Definition and Provisioning |
| SDTA | South Dakota Telecommunications Association |
| SDTN | Saratov Digital Telephony Network |
| SECABS | Small Exchange Carrier Access Billing System |
| SEFL | Single-Ended Fault Locating |
| SES | Severely Errored Seconds |
| SETIT | Sciences of Electronic Technologies of Information and Telecommunications |
| SETIT | Sciences of Electronics Technologies of Information and Telecommunications |
| SF | Single Frequency |
| SF | SuperFrame |
| SG | SuperGroup |
| SGCP | Simple Gateway Control Protocol |