AT&T MERLIN LEGEND Release 3.1 System Planning Manual page 225

Assigning Lines/Trunks to Data and Video Stations
— 400 (LS lines/trunks only)
— 800 (LS lines/trunks only)
— 408 GS/LS-MLX
— 800 GS/LS-ID
Analog/Digital Tie. This trunk type "ties" two telephone switching
systems together, providing access to all telephones or data equipment
on each system. Analog Tie trunks are used for data communication with
modem data stations connected to a system at a different location, such
as a different floor of a building, a different building, or a different city or
state. Analog Tie trunks connect to a jack on a 400EM module in the
control unit. Video calls are not made over analog Tie lines/trunks.
Digital Tie trunks are used for digital data communications, such as G4
FAX and videoconferencing, with digital data/video stations connected to
a system at a different location, such as a different floor of a building, a
different building, or a different city or state. Digital Tie trunks are
emulated by T1 facilities connected to a 100D module in the control unit.
Video and digital data calls may be made over digital Tie lines/trunks.
Direct Inward Dial (DID). Incoming calls reach specific individuals or
facilities in the system without the help of a system operator. DID trunks
are available only in Hybrid/PBX mode. A DID trunk is used to receive
incoming calls from outside modem data stations. It is not used for
outgoing calls. A DID trunk connects to a jack on an 800 DID module in
the control unit. Video calls are not made over DID lines/trunks.
DS1 (Digital Signal 1). This facility carries digital signals in the DS1
format. A DS1 facility can be used for communication with outside digital
or modem data stations, including video systems. A DS1 facility connects
to the jack on a 100D module in the control unit. Even though there is
only one physical jack, the 100D module supports up to 24 logical
endpoints for voice and data calls; each DS0 channel in the DS1 signal
corresponds to a trunk or logical ID.
A DS1 facility provides either T1 (including T1 Switched 56 for digital
data/video calls) or PRI access:
T1 (factory setting). The 24 channels on a T1 facility can be
programmed individually in any combination to emulate a loop-start,
ground-start, E&M tie, DID, or Switched 56 digital data trunk, so a
single 100D module can replace 24 outside lines/trunks. When T1
Switched 56 service is used, high-speed video connections at data
rates of 56-kbps per channel (112-kbps for 2B Data) are possible.
Data Communications
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