ATT System 25 Reference Manual

DS1 Facility Interface
When digital signals are transmitted over a network of digital communications links, switching
nodes, multiplexers, and transmission interfaces, all entities must be synchronized. This is
referred to as network synchronization.
For synchronous transmission,information is transmitted to the transmission facility at a
fixed rate. Each bit occupies a fixed unit time interval. All significant transitions must
correspond to multiples of the fixed unit time interval.Message and frame...

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:
l The other vendor’s PBX must provide a DS1 interface as specified by AT&T.
l The other vendor’s PBX must provide at least one of the line
signaling options provided by the System 25.
l The other vendor’s PBX must implement the digital loss plancoding, framing, and
specified in EIA RS-
464/PN1378.
l The other vendor’s PBX must either maintain a...

DS1 Facility Interface
The trunks terminating on a 4ESS switch must be administered as either tie or direct inward
dialing trunk types. The tie trunks can be either one-way or two-way; either immediate start,
wink start or delay dial. The DID trunks are incoming only and wink start or immediate start.
Some 4ESS switches do not provide secondary dial tone. It is recommended that System 25
provide the secondary dial tone.Secondary dial tone can be provided through the Automatic
Route Selection (ARS)...

FEATURES AND SERVICES
synchronized to the AT&T Reference Frequency, then it can be used as the synchronization
reference for the System 25.
DS1 Interface Circuit Pack
The TN767 circuit pack is the principal hardware element connecting System 25 to the T1
facility interface.Two DS1 circuit packs may be mounted in the System 25 cabinet(s). Each
DS1 facility interface CP supports up to 24 trunks (23 if common channel signaling is used).
The TN767 CP emulates the TN747 CO trunk CP, the TN753 Direct Inward...

DS1 Facility Interface
Administration Requirements
The administration of DS1 interface CP is completed by accessing the Port, High Density
Circuit (HI D CKT), and System entries of the main administration menu.
The items to be administered under Port include (default):
l Assign 24 DS0 channel slots
l Assign port type, the TN767 CP supports the following port types:
— 201
— Single line tip/ring station without a message waiting light
— 7xx —Ground start trunks
— 8xx —Loop start trunks
— 9xx —
Direct...

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The items to administered under System include (default):
l Assign Primary Synchronization Source (No slot)
l Enable Automatic Synchronization Source Switching (enabled)
Hardware Requirements
Requires a TN767 CP plus ZTN131. The TN767 CP provides 24 ports.
DS1 Interface Connection Information
Detailed connection information is provided in the following figures:
l Figure 2-14—
Direct DS1 Connection Between Adjacent System 25 Cabinets
l Figure 2-15—
Direct DS1 Connection Between...

DS1 Facility Interface
131O FEET MAXIMUM
CABLING DISTANCE
SYSTEM 25
SYSTEM 25
TN 767C6D CONNECTORCABLE (NOTE)TN767
< >
NOTE:
Figure 2-15. Direct
Apart,
FOR DISTANCES OVER 50 FEET (15.2 M)
USED C6E CONNECTOR CABLE(S) BETWEEN
C6C CONNECTOR CABLE AND DS1 TIETRUNK CIRCUIT PACK.
DS1 Connection Between System 25 Cabinets (Located 1310 Feet
Maximum)
S25
TN767CSU
CSU
DSX-1
DSX-1
OFFICE
OFFICEDS1
REPEATER
REPEATER
655 FEET
MAXIMUM
Figure 2-16. System 25
3000 FEET OR LESS
655 FEET
MAXIMUM
Connection to DS1...

FEATURES AND SERVICES
S25
TN767CSU
DSX-1
PROTECTION(NOTE)CIRCUIT
655 FEET
REPEATERED
MAXIMUM
DS1 LINE
CSU
DSX-1PROTECTIONDS1(NOTE)CIRCUIT
655 FEET
MAXIMUM
NOTE:USE OF THE OFFICE REPEATER IS OPTIONAL DEPENDING
UPON THE DISTANCE TO THE FIRST T1 REPEATER
Figure 2-17. System 25 Connection to DS1 Facility Located 4311 Feet or More Away
S25
TN767DSX-1T1 LINE
REPEATER
6000 FEET
3000 FEETOR LESS
655 FEET
MAXIMUMOR LESSCSU
CSU
DSX-1T1 LINEDS1REPEATER
655 FEET3000 FEET
MAXIMUMOR LESS
Figure 2-18.System 25...

DS1 Facility Interface
MICROWAVE
INTERFACEMICROWAVE
INTERFACE
S25
TN767
DSX-1DSX-1
DS1
655 FEET
MAXIMUMLIGHT-GUIDE
LIGHT-GUIDE
INTERFACEINTERFACE
INFRAREDINTERFACEINFRAREDINTERFACE
ANY DSX-1
INTERFACE
ANY DSX-1INTERFACE655 FEET
MAXIMUM
Figure 2-19.
System 25 Connection to DS1 Facility (Non-Metallic Transmission Interface)
SYSTEM 25
TN767C6C
CONNECTOR
CABLE (NOTE)
< >
NOTE: FOR DISTANCES OVER 50 FEET (15.2 M)USED C6E CONNECTOR CABLE(S) BETWEENC6C CONNECTOR CABLE AND DS1 TIETRUNK CIRCUIT PACK.551 CSU
TB1...

FEATURES AND SERVICES
Data Call Setup
This feature allows a user to originate calls from
25 provides three methods of data calling:
l Dialing from a data terminal, which is
feature description.a data terminal or a voice terminal. System
described in the“Data Terminal Dialing”
l Setting up data calls from a voice terminal,which is described in the “Transfer to
Data” feature description.
l Setting up data calls (or voice calls) for another terminal from a data terminal, which
is described in the...