Class 1

In the traditional public switched telephone network (PSTN) hierarchy, a regional toll center.

The 10 Class 1 offices that existed prior to the breakup of the Bell System served to interconnect Class 2

offices, or sectional toll centers. At the end of 2001, seven remained in the United States, and two in Canada. See Figure C-3. See also Bell System, Class 2, and PSTN.

• priority ringing
• PRI (Primary Rate Interface)
• privacy
• privacy key management (PKM)
• private automatic branch exchange (PABX)
• private branch exchange (PBX)
• Private Integrated Services Network (PISN)
• Private IP
• private IP address
• private key encryption
• private paging operator (PPO)
• private port
• Private Signaling System No. 1 (PSS1)
• Private UNI (Private User Network Interface)
• privatize
• procedure
• program
• program
• program file
• program file
• progressive scanning
• propagation
• propagation delay
• property management interface (PMI)
• proprietary