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Glossary
This glossary is intended to better serve you in determining
all your voice, data and telecommunication equipment needs.
If you have any additional questions or any of these terms
need clarification, please call our Customer Service Department
at 215.348.1588.
J Hook
J-shaped pieces of bent metal used to hold cables in
an equipment rack.
Key Service Unit (KSU)
A small metal cabinet that contains all of the electronics
of a business key telephone system. The KSU fits between
the lines coming in from the central office and the lines
going to the individual phones. The KSU should be in a
well-ventilated location because it gets very hot. It should
be near a power outlet that is dedicated to it (other devices
such as computers, TVs, vacuum cleaners, etc. could affect
it)
LAN – Local Area Network
A communications network connecting personal computers,
workstations, printers, file servers, and other devices
inside a building or campus.
Least Cost Routing (LCR)
A telephone system feature that automatically chooses
the "least cost" long distance and local lines
to send the call on. The caller typically dials 9 and then
the 10-digit telephone number. The call is then routed
over the least costly service.
Lines
In traditional telecom, a line is an electrical path (2
wires) between a phone company central office and a subscriber.
LNP - Local Number Portability
The ability to change your phone company and still keep
your dame phone number.
Loop Start Telephone (LST) Board
With loop start, you seize a line by bridging through
a resistance the tip and ring (both wires) of your telephone
line. The Loop Start trunk is the most common type of trunk
found in residential installations. The ring lead is connected
to a -48V and the tip lead is connected to 0V (ground).
To initiate a call, you form a "loop' ring through
the telephone to the tip. Your central office rings in
a telephone by sending an AC voltage to the ringer within
the telephone. When the phone goes off-hook, the DC (Direct
Current) loop is formed. The central office detects the
loop and the fact that it is drawing DC current and stops
sending the ringing voltage.
Main Distribution Frame (MDF)
A wiring arrangement that connects the telephone lines
coming from outside on one side and the internal lines
on the other. A main distribution frame may carry protective
devices as well as function as a central testing unit.
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