Telos Zephyr Xstream - Manual (Page 366)

USER’S MANUAL
Appendix 10 – Glossary 354
ISDN 30 A term used in Europe for ISDN PRI. Also called S2M See PRI.
ISG – Incoming Service Grouping A Hunt Group. See Hunt Group
IXC‐ IntereXchange Carrier See IEC
Kbps KiloBits Per Second. Measure of digital channel capacity.
Key Telephone System A system that allows multiple telephones to share multiple pre‐
determined telephone lines. The system provides indicators to allow the user’s to understand
the status of each line available on a given phone. In its most basic form it is USER’S MANUAL up
to the user to provide the intelligence to select an unused line, or answer a ringing line, for
example. The Telos 10, Direct Interface Module, One‐ x‐ Six, TWOx12 and Series 2101can be
classified as Key Telephone Systems. See also PBX.
LATA‐ Local Access and Transport Area The area within which calls are routed by your Local
Exchange Carrier (LEC). Under the divestiture of the Bell System calls going outside of this area
must be handled by an Interexchange carrier (IEC). With the latest round of de‐ regulation the
usual IEC companies are being allowed to compete in the IntraLATA long distance market and
LECs are beginning to be permitted to handle InterLATA calls.
LDN‐ Listed Directory Number When a number of Telco channels share the same hunt group, it
is customary to give out only one phone number for the group, although generally each channel
will have its own number. The number given out is the “Listed Directory Number” since that is
the number that would be listed in the Telephone Directory and given to customers. Sometimes
called a Pilot Number. See also DN and Hunt Group.
LE ‐ Local Exchange. European term for Central Office. See CO.
LEC‐ Local Exchange Carrier Your local telephone service provider which is either an RBOC or an
Independent. In other words, a traditional phone company. In contrast to CLEC or IEC.
Line An electrical connection between a telephone service provider’s switch (LEC or CLEC) and a
telephone terminal or Key system. An electrical connection between a telephone service
provider’s switch and another switch is technically called a trunk. Note that some type of
physical lines offer more than one channel. I.E. a BRI circuit has 2 channels, called B channels.
This term is a confusing one, so we try to avoid using it. See Channel. See also Station Line.
Line card The circuit in the Telco switch to which your line is connected. On an ISDN circuit the
line card performs a role analogous to the NT1 in adapting to and equalizing the circuit to
establish OSI Layer 1.
Line Coding, T1 The clock signal for T1 is derived at the far end from the data bits themselves.
Therefore, T1 lines have certain restrictions as to the data allowed. No more than 15 zeros shall
be sent in a row; and average density of 12.5% ones must be maintained. The CSU is responsible
to ensure that these requirements are met. The line encoding method, AMI or B8ZS determines
exactly how these requirements are met while still allowing recovery of the original data at the
far end. Your Telco will determine the method used on a specific circuit. B8ZS is preferred. E1
circuits have similar restrictions. HDB3 is preferred for E1 circuits.
Listed Directory Number See LDN
Line Encoding, T1 See Line Coding, T1.