Class 1

Class 1

Regional Center

Class 2

Sectional Center

Class 3

Primary Center

Class 4

Toll Center

Class 5

End Office

High-Usage Group

• Secure Hypertext Transport Protocol (S-HTTP)
• Secure Multipurpose Internet Mail Extension (S/MIME)
• Secure Sockets Layer (SSL)
• security
• security
• security
• security management
• seed rod
• segment
• segmentation
• segmentation and reassembly (SAR)
• seizure
• selective call acceptance
• selective call block
• selective call forwarding
• selective call rejection
• selective ringing
• selector
• selenium
• self-healing
• self-learning bridge
• semiconductor
• send and pray
• sender
• Sequenced Packet Exchange (SPX)