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108 | Appendix 2
system was devised by the National ISDN User’s Forum and
Bellcore to simplify ordering new ISDN lines in the USA and
Canada. Using a single code specifies all line specifications. e
Telos Zephyr, ZephyrExpress, TWO, and TWOx12 support IOC
package “S”. Search for document NIUF 428-94 at NIUF’s web
page http://www.niuf.nist.gov/ for more information.
ISDN - Integrated Services Digital Network- A relatively new
and highly flexible type of telephone service which allows dialing
on digital channels with multiple bi-directional “Bearer” channels
each with a capacity of 56 or 64 Kbps and a single bi-directional “D
channel”. See BRI and PRI.
ISDN Protocol - e “language” used for communication between
the Telco’s switch and the customer’s Terminal Adapter. Each
ISDN circuit has one protocol, and the protocol has no effect on
where or whom one may call. See ETS 300, National ISDN, and
Custom ISDN.
ISDN 2- A term used in Europe for ISDN BRI. Also called S.
Not to be confused with National ISDN-2. See BRI.
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. e system pro-
vides 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 up to the
user to provide the intelligence to select an unused line, or answer
a ringing line, for example. e Telos 10, Direct Interface Module,
One-x-Six, TWOx12, Nx12, and Series 2101can be classified as
Key Telephone Systems. See also PBX.
L ATA - Local Access and Transport Area. e 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 chan-
nels 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. e number given out is the “Listed Direc-
tory 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.
POTS lines (or a 2-wire intercom) to a four-wire system (sepa-
rate send and receive paths) such as used in the pro-audio world.
While this task is theoretically quite simple, the fact the impedance
of most phone lines varies widely across frequency complicates
matters. e Telos 10 telephone system was the first practical DSP
based hybrid and applied the then brand-new technology to this
problem.
IEC - 1) InterExchange Carrier. “Long Distance” carrier. Handles
Interlata and interstate calls. Also referred to as IXC. 2) Interna-
tional Electrotechnical Committee. A European standards body
best known for the power plug now used throughout the world for
AC power cords for use on office equipment and computers.
ILEC – Incumbent Local Exchange Carrier. A local Exchange
Carrier which entered the marketplace before the enactment of the
1996 Telecom act;. i.e. a telephone company which is neither an
Indi nor an RBOC. See LEC and CLEC.
IMUX – See Inverse Multiplexing
In Band Signaling- A signaling system where network information
such as address and routing information are handled over the com-
munications (voice) path itself. Usually the information is represent-
ed in the form of audible tones, however DC loop current signaling
also qualifies as In Band Signaling. See also CCIS.
Incumbent Local Exchange Carrier. See ILEC. See also CLEC
& LEC
Independent – Any of the phone companies in existence at the
time of divestiture that were not affiliated with the Bell System. See
RBOC, LEC, and CLEC.
Indi- See Independent.
Interconnect Company- A vendor of telecommunications CPE
other than a BOC or AT&T. is term was originated by AT&T
and was meant to be derisive towards the fledgling industry when
the courts said it was OK for end users to buy equipment from
someone other than the Bell System. is industry flourished, in
spite of AT&T’s disdain, and ironically, the RBOCs were not al-
lowed to sell CPE under the terms of the break up of AT&T. With
the current state of deregulation, the RBOCs are slowly re-entering
this business.
Interexchange Carrier- See IEC
Interwork- e ability of two different type of networks to com-
municate seamlessly. For example, ISDN can interwork calls to both
the POTS network and the Switched-56 network.
Inverse multiplexing- A method of breaking apart and later com-
bining 2 data streams that does not involve the telephone network.
Inverse multiplexing is the most common way of achieving this
function in Codecs operating at 112 or 128kbps over ISDN.
IOC Capability Packages - ISDN Ordering Code system. is