Lines/Trunks - AT&T MERLIN LEGEND System Reference Manual

Functional Description

Lines/Trunks

Loop-Start Line/Trunks
Ground-Start Lines/Trunks
Tie Trunks
This section describes the functioning of the lines/trunks in the system.
Loop-start lines/trunks are the standard for home and small business Key
systems. They are less expensive in some areas but have certain limitations:
They do not protect against glare. (Glare occurs when a person tries to make
an outside call on a line/trunk at the same time an incoming call is being
received on that line/trunk.)
They can have higher cable losses and, therefore, transmissions of less
quality than ground-start lines/trunks.
They cannot assure secure toll restriction.
Ground-start lines/trunks are outside lines/trunks used by some businesses
(such as hotels or motels) where improved signaling is important. The improved
signaling of ground-start allows more secure toll restriction.
In addition, ground-start lines/trunks prevent glare. Ground-start lines/trunks
also provide cable losses
The following types of outside lines/trunks can be either ground-start or loop-
start
basic lines/trunks (used for both local and long-distance calls)
WATS (wide area telecommunications service)
800 service (In-WATS)
foreign exchange (FX)
Tie trunks provide private communication between two systems. Tie trunks "tie"
the two systems together, making it seem that all the telephones are on the
same system.
Tie trunks provide efficient communication between systems at different
locations. These locations can be different floors of the same building, different
buildings in the same campus, or different cities or states.
Tie trunks can be added to the system via the 400EM module. The 400EM
module has four ports that must be programmed individually by selecting trunk
options via system programming and setting the DIP switches (located on the
front of the module) for E & M protected, E & M unprotected, or simplex
signaling mode.
4.5 dB.
Lines/Trunks 4-23