AT&T MERLIN LEGEND Release 2.0 Equipment And Operations Manual page 137

Lines and Trunks
Analog Tie-Trunk Connection
In an analog tie trunk connection, the system's control unit is connected
to the control unit of another system via a 400EM module. if both
systems are on the same premises, this module can be connected
directly to the other system if the other system has similar tie-trunk
facilities
For off-premises connection, the 400EM module can be connected via
the telephone company's facilities to another system.
An analog tie-trunk connection can be administered for two-way traffic or
for one-way traffic (incoming or outgoing). The one-way mode prevents
blocked calls caused by glare.
Digital Emulated Tie-Trunk Connection
In a digital emulated tie-trunk connection, the system's control unit is
connected to the other system's control unit via a 100D line/trunk module
programmed for T1-type transmission. A back-to-back connection from
one DS1 facility to the other can be used when the total cable distance is
less than 1300 feet (396 meters). To reach a remote system, the DS1
facility connects via a channel service unit (CSU) to the telephone
company's facilities.
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.
400EM Module Options
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,
The following tie-trunk options need to be programmed via system
programming, See Tables 3-1 and 3-2 for information on DIP switch settings.
E&M Signaling Type
— Type 1 Standard (the factory setting)—used when tie trunks are
— Type 1 Compatible—used when tie trunks are connected directly
— Type 5—used when tie trunks are connected directly to a system
connected to the other system through the local telephone
company.
to a system that uses type 1 S signaling and is located near this
system.
that uses Type 5 signaling and is located near this system.
Tie Trunks 3-3