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Appendix A: Glossary
A-6
Network Service A collection of spans from a fixed service provider. Network
services can be any of the following types:
• Private Network
• Public Utility, including:
• Long distance service
• Local service
• PTT
• PBX; local switchboard leased line
Null modem
cable
A serial cable designed to eliminate the need for
communication equipment when two digital devices are
directly connected to each other.
Port One of 23 channels in a T1 PRI; one of 24 channels in a T1
leased line; or one of 30 channels in an E1 PRI.
POTS Plain Old Telephone System. The conventional analog
telephone line.
PRI Priority Rate Interface. An ISDN interface designed for high
volume data communication. Consists of 23 B channels of 64
Kbps each and one D channel of 64 Kbps. In Europe, the PRI
line provides 30 B channels + one D channel.
QCIF Quarter CIF. A video format with image size of 176x144 pixels
that transmits 9.115 Mbps at 30 frames per second (a quarter
of the capacity of CIF). See also CIF.
RS-232 A standard for serial interface connection.
SIP Session Initiation Protocol. An application-layer protocol
designed to work over IP networks.A SIP service defines the
properties and the IP addresses of the SIP network
components.
Span An ISDN line or leased line. A span may be of either T1
(United States) or E1 (Europe) type. Also called a circuit.
Switched 56 line A line using protocols pre-dating the ISDN protocols; also
called a robbed bit signaling line or a pre-ISDN line.
Abbreviation/
Term
Explanation