Instruction manual

FEATURES AND SERVICES
Non-AT&T Digital PBX Endpoints
To determine if the System 25 can be connected to another vendor’s PBX, several items
must be verified:
● The other vendor’s PBX must provide a DS1 interface as specified by AT&T.
● The other vendor’s PBX must provide at least one of the line
signaling options provided by the System 25.
● The other vendor’s PBX must implement the digital loss plan
coding, framing, and
specified in EIA RS-
464/PN1378.
● The other vendor’s PBX must either maintain a stratum 4
synchronizing to System 25.
This list is not exhaustive. Many vendors have certification testing
products.
AT&T Analog PBX Endpoints
The System 25 DS1 interface can be connected to an analog PBX
clock or be capable of
programs for their DS1
(such as a Dimension®
PBX or other vendor analog PBX) provided a D4 channel bank is used. The channel bank
demultiplexes the 24 DS0 digital channels and converts each to analog form. The analog
form supports a variety of telephony signaling arrangements. If a D4 channel bank is used,
D4 framing, robbed-bit signaling, and ZCS line coding must be used.
Analog Off-Premises Station Endpoints
The System 25 DS1 interface can be connected to 24 analog off-premises stations provided
a D4 channel bank is used.
Public Network Connection
Public network endpoint connections include central offices, Digital Access and Cross-
Connect (DACS) system frames, and toll offices.
Note:
Most public network connections require a Customer Service Unit (CSU) to
be installed at the PBX location. The CSU provides proper termination of the
circuit (includes
network protection
and FCC compliance), signal
regeneration, and loopback testing. A CSU is required at each PBX location
when connecting to ACCUNET™ T1.5 service.
4ESS Toll Switch Endpoint
This connection is called Special Access connection.
The physical connection is made either
directly from the System 25 location to the 4ESS toll switch or from the System 25 location
to a central office (a
“nailed-up” connection) and then to the toll switch. In either case, toll
calls go directly from the System 25 to the AT&T Communications toll network.
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