Hx1-Hx2 Manual-1.4.1 - Telos

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Loop- The telephone circuit from the CO to the customers premises. Generally refers to a
copper cable circuit.
Loop Current Disconnect Supervision - Another name for CPC. See CPC.
Loop Qualification- Process of actually measuring the loss on a prospective ISDN line to see if
it can be used for ISDN service. The actual loss on the line (usually measured at 40 kHz) is the
determining factor whether ISDN service can be offered without a repeater. Generally ISDN
or DSL is available up to 18,000 feet from the serving Central Office. It may not be available
within this range, or may be available further from the CO. Only a loop qualification can tell for
sure. Not all Telcos will extend ISDN lines with repeaters.
Loop Start Line - A plain old telephone line. The telephone terminal signals the “off hook”
condition by allowing DC current to flow. See Ground Start Trunk. See also Glare.
Loop Start Trunk – A plain old telephone line connected to a PBX switch. See Loop Start
Line. The PBX signals the “off hook” condition by allowing DC current to flow. Ground Start
Trunks are generally preferred for use on PBXs to prevent glare. Also, most trunks are considered
“designed circuits”. That means that only a specified amount of loop loss is permissible, and
that the telephone company is required to deliver the trunk to the customer at a given audio
level. At the time of this writing, analog trunks are rapidly becoming less common as they are
expensive to design, provision and maintain. See Ground Start Trunk. See also Glare.
LOS- Loss Of Signal. An LED or other indicator that illuminates if a signal is absent. This
terminology is commonly used with T-1 equipment. See Red alarm.
LT - Line Termination - The electrical and protocol specifications for the Central Office end of
an ISDN line. If you wish to connect an ISDN terminal (such as a Zephyr Xstream) to a PBX
the PBX must support LT ISDN. See also NT and Line Card.
Lucent Technologies- Company that made the former AT&T 5ESS switch, as well as various
other piece of Telco gear and semiconductors. Lucent was split off from AT&T in 1996.
Lucent’s PBX division was spun off in 2001 as AVAYA.
MCLD- Modifying Calling Line Disconnect. The parameter on the Lucent 5ESS switch that
determines if CPC is active. Should be set to “Yes” if CPC is required. See CPC.
National ISDN (USA & Canada)- The US “standardized” multi-platform ISDN protocol. The
first version is National ISDN-1. As of mid 1996 National ISDN-2 has been implemented in
some areas and is fully backward compatible with National ISDN-1.
NCTE – Network Channel Terminating Equipment. NCTE is a general term that can be applied
to a CSU or NT1 or other equipment terminating a digital line at the customer’s premises.
In many countries, the NCTE is provided by the Telco. The USA is not one of those countries.
Network Channel Terminating Equipment. See NCTE.
Network Termination - See NT.
NIU – Network Interface Unit, a line powered, telephone company owned, interface card that
provides a remote controlled loopback function, some error monitoring and signal level conditioning.
It’s typically a box on the wall with some lights, that has at least one RJ45 jack, and a
cable going to either the RJ21x block or other demarc. The NIU converts the incoming 2 pair
line to an RJ45 T1 or PRI line, you need a CSU/DSU between it and your equipment to handle
the level conversion and provide your own loopback capability. The NIU and the cable going to
it are the phone company’s property and their maintenance responsibility. Most often the NIU
(or sometimes called simply “NI” or “Smart Jack”) is located in a locked cabinet. Also a nice
little college in Illinois.