ATT DEFINITY Communications System Generic 3 Instructions Manual

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Issue  3   March 1996
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Electronic Tandem Network (ETN)
An Electronic Tandem Network (ETN) is a hierarchical network of privately owned 
trunk and switching facilities that can provide a cost-effective alternative to toll 
calling between locations. An ETN consists of tandem switches, the intertandem 
tie trunks that interconnect them, the access or bypass tie trunks from a tandem 
switch to a main switch, and the capa bility to control call routing over these 
facilities. A Main/Satellite/Tributary configuration can be served by an ETN or a 
DCS can also be p art of an ETN.
The system can serve as an ETN tandem switch.
Within an ETN each location is i dentified by a unique private network office code. 
With G3i, this private network office code may be of the form RN, RNX, RX, XX, 
RNX, RXX, XXX,  and RNXX,  depending on administration (R  = digits 2 through 9, 
N = di gits 2 through 9, and X = digits 0 through 9). After accessing the ETN, the 
user simp ly dials the private network office code plus the d esired extension 
number, for a total of ten digits or less.
Private network office codes are unique within an ETN. Private network office 
codes are assigned when the ETN is established. When  Direct  Inward Dialing 
(DID) is provided by the local central office, the extension numbers (last four 
digits of the number) will match. Network Inward Dialing (NID) is the ETN 
equivalent of DID and  can be provided without DID.
The software program that controls call routing over an ETN is called Automatic 
Alternate Routing (AAR). AAR not only determines the route for a call, but, 
through the Facilities Restriction Level (FRL) function, d efines up to eight levels of 
calling privileges for users of the ETN. Another function of AAR, Subnet Trunking, 
can convert an on-network number to a public network or international number. 
This function is useful when all on-network routes are busy or are not provided. 
The details of Automatic Alternate Routing, Facilities Restriction Level, and 
Subnet Trunking are provided in this chapter.
AAR digit conversion can be used to convert private network numbers to other 
private network numbers or public network numb ers. This allows the system to 
steer some AAR calls to other switches in the private network or, by changing 
specific dialed  digits to a p ublic network number, eventually route some calls via 
ARS. Also, unauthorized private network calls can be route d to an attendant or 
receive intercept treatment. Details on AAR digit conversion can be found in the 
Automatic Alternate Routing feature description.
Distributed Communications System (DCS)
A Distributed Communication System (DCS) is a cluster of private 
communications switches (nodes) interc onnected among several geographic 
locations. These switches can be either a DEFI NI TY Generic 1, DEFINITY 
Generic 2, DEFI NI TY Generic 3, System 75, System 85, or DIMENSION PBX.  
						

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Refer to the System Parameters table In Appendix A for the node limitations of 
each system type.
An attribute of a DCS configuration that  distinguishes it from other networks is 
that it appears as a single switch with respect to certain features. This provides 
simplified dialing procedures between locations, as well as the convenience of 
using some of the system’s features between locations. DCS is particularly useful 
if there is frequent interlocation calling.
Each DCS node is connected with every other DCS node by tie trunks or 
ISDN-PRI trunks (DEFINITY Generic 3) for voice communications and data links 
that send and receive control and feature information. However, each DCS node 
does not have to be directly connected to every other node. Communication may 
be through a DCS tandem node. The data links and voice channels may be 
directly between nodes or may pass through a tandem node. Nodes that cannot 
serve as a tandem node (that is, those that cannot receive information from one 
node and pass it on to another node) are called endpoints (or endpoint nodes). 
Nodes that can pass information are simply referred to as nodes. DEFINITY  
Generic 3i can serve as either an endpoint node or a regular (tandem) node. 
Figure 2-6 shows a typical DCS configuration.
A DCS can consist of all end points. That is, each node in the DCS may be 
directly connected by data links and voice channels with every other node in the 
DCS.
Some of the applications of the DCS configuration are as follows:
nIn a ‘‘campus environment’’ that has two or more separate buildings and 
the nodes are connected by local cable.
nIn a larger area such as a city, several states, or even the entire country, 
where the nodes are separated by distances too great for local cable and 
may be connected to different central offices.
A DCS has the property of ‘‘transparency’’ with respect to inside calling and 
some features. Transparency is the ability of the system, from the user’s 
standpoint, to operate across several nodes in the same way it does at the local 
node. This allows users to dial from any terminal to any other terminal within the 
DCS without regard for which nodes are involved. Likewise, transparency allows 
certain voice features to b e used across nodes. 
						

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Figure 2-6. Typical Distributed Communications System
Some voice features have transparency in a DCS configuration. The following 
voice features have unique aspects in a DCS environment and are d esc rib e d in 
detail in this book.
nDCS Alphanumeric Display for Terminals
nDCS Attendant Call Waiting (described under DCS Call Waiting)
nDCS Attendant Control of Trunk Group Ac cess
nDCS Attendant Direct Trunk Group Selection
nDCS Attendant Display
nDCS Automatic Callback
nDCS Automatic Circuit Assuranc e
nDCS Busy Verification of Terminals and Trunks
nDCS Call Coverage
TIE TRUNKS
SYSTEM B
ENDPOINT NODE
TIE TRUNKS
DATA LINKCO
OUTSIDE
TRUNKS
MAIN LOCATION
BRANCH
CO
OUTSIDE
TRUNKSRELEASE LINK TRUNKS*DATA LINK
TIE TRUNKS
DATA LINK
CENTRALIZED
ATTENDANT SERVICE
CO
CO
OUTSIDE
TRUNKS OUTSIDE
TRUNKS
SYSTEM D (SYSTEM A)
SYSTEM C
ENDPOINT NODE
* REQUIRED ONLY IF THE NETWORK HAS OPTIONAL
CENTRALIZED ATTENDANT SERVICE. RELEASE
LINK TRUNKS ARE NOT REQUIRED FOR DCS.
WITH V2, SYSTEM 75 CAN ONLY BE AN ENDPOINT
IN DCS. 
						

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nDCS Call Forward ing All Calls
nDCS Call Waiting — Termination (described under DCS Call Waiting)
nDCS Distinctive Ringing
nDCS Leave Word Calling
nDCS Multi-Appearance Conference/Transfer
nDCS Priority Calling (described under DCS Call Waiting)
nDCS Trunk Group Busy/Warning Indication.
nEnhanced DCS (described under Enhanced DCS).
Abbreviated Dialing and Last Numb er Dialed also have transparency in a DCS 
configuration. These features o perate the same in a DCS as they do at a single 
switch.
A DCS cluster can consist of up to 64 nodes. Since AUDIX and the Call 
Management System (CMS) and  ISDN-PRI each require the same data link 
facilities as a node, each of these included in the system reduces the number of 
available d ata links, which, depending on the system configuration, may reduce 
the maximum number of nodes.
Use of the DCS over the ISDN-PRI D-channel feature on the other hand, may 
increase the maximum number of nodes. (Note that on G3r, ISDN-PRI d oes not 
require the same data link facilities as a node.)
DCS Message Hopping lets a DCS message route through an intermediate node 
without tandeming an associated trunk call. This is accomplished through the 
use of hop channels. The system provides Message Hopping through up to two 
hops.
DCS transparency is more restricted when the tandem node is an Enhanced 
DIMENSION PBX or a System 85 Release 2 Version 1 than when it is a System 85 
Release 2 Version 2, or later, or a DEFINITY  Generic 2.1, or later. (See the DCS 
Alphanumeric Display for Terminals and DCS Leave Word Calling features.)
Certain feature capabilities are unique to a particular type of node (for example, 
a D EFI NITY  Generic 3 endpoint node). Therefore, a d etailed feature description 
should be consulted for each type of node.
The Centralized Attendant Service (CAS) feature can be used as an advantage in 
DCS networks where all attendants are at one node. CAS reduces traffic volume 
on interconnecting tie trunks caused by incoming attendant-seeking calls at the 
endpoint nodes. DEFI NIT Y Generic 3 can serve as the main location for CAS 
attendants. Centralized Attendant Service capabilities are given in detail in this 
manual.
With DCS Call Coverage (G3V4 and later releases), calls to an extension on one 
system can be covered by extensions administered as coverage points on  
						

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remote systems. DCS Call Coverage provides transparenc y across systems for 
the Call Coverage feature.
Main/Satellite/Tributary
Figure 2-7 shows a Main/Satellite/Tributary configuration. It can function 
independently or serve as an ETN access arrangement. For a Main/Satellite 
configuration, attendant positions and public network trunk facilities are 
concentrated at the Main, and calls to or from satellite locations pass through the 
Main. To a caller outside the Main/Satellite complex, the system a p pears to be a 
single switch with one Listed Directory Number. This is accomplished with the 
optional Uniform Dial Plan software.
Tributary and Satellite locations are similar except that a Tributary has one or 
more attendant positions and its own Listed Directory Number.
DEFI NI TY Generic 3 can serve as a Main, Satellite, or Tributary.
A small business can start with a single Main/Satellite or Main/Tributary complex 
and add trunk and switching facilities as the business grows. In this situation, tie 
trunks connect the main locations within an urban area and intercity traffic is 
routed via the p ublic network. This arrangement favors a medium-size 
organization or one that has small isolated locations where the intercity traffic is 
too small to justify the cost of tie trunks.
Figure 2-7. Main/Satellite/Tributary Configuration
TIE TRUNKS
SATELLITE TRIBUTARY
SYSTEM SYSTEM
MAIN 
						

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Trunking
Trunking is the use of communications links to interconnect two switching 
systems, such as connecting the switch to a local central office or to another 
switch. These links, called trunks, can be grouped together in Trunk Groups 
when all the trunks in the group perform the same function. This g rouping 
simplifies administration since the required service characteristics (parameters) 
are assigned to the group rather than to each trunk. Grouping also simplifies call 
processing. Calls requiring a trunk are routed to the appropriate trunk group and 
an idle trunk, if available, is selected from the group.
There are analog trunks and digital type trunks. The type of signal is specified for 
each trunk in the list below. The following types of trunk groups can b e used with 
the system:
nAuxiliary — Provides internal trunk a p plications for features such as 
Loudspeaker Paging and Music-on-Hold. This is an analog signal.
nCO — Provides a link with the local Central Office (CO) for Direct Outward 
Dialing (DOD) and manually completed incoming calls, not Direct Inward  
Dialing (DID) calls. The signals may be analog or digital
nDirect Inward Dialing (DID) — Provides a link with the local CO that is only 
usable for incoming calls and allows the CO to send d igits to the PBX so 
the call can be routed to a particular station. The signal can be analog or 
digital
nDirect Inward/Outward Dialing (DIOD) — Provides a link with the local CO 
that allows digits to be sent in either direction for incoming and outgoing 
calls. The signal can be either analog or digital
nDS1/E1 Tie Trunk — Provides for two types of digital tie trunk interfaces:  
Voice-Grade DS1/E1 and Alternate Voice/Data (AVD) DS1/E1 tie trunks. 
The Voice-Grade DS1 tie trunks are an alternative to four-wire analog E&M 
tie trunks and may be used to interface with other properly-equipped 
switching systems. AVD DS1/E1 tie trunks permit alternate voice and data 
calling between a System 75, DEFI NIT Y Generic 1, DEFI NI TY Generic 3 
and a System 85 or DEFINITY  Generic 2. DS1/E1 tie trunks also can be 
used with Release Link trunks for Centralized Attendant Service, and can 
be used with AT&T unbanded telecommunications service. (d igital signal)
nFX — Provides a link with a CO other than the local CO. (analog or digital 
signal)
nISDN-PRI — Provides end-to-end digital connectivity and supports a wide 
range of voice and non-voice services. Calls to a variety of switched nodal 
services and calls destined for different inter-exchange carriers can be 
processed. (digital signal)
nTie a n d Release Link — Provide a link with another private switching 
system for calls between the systems. Release link trunks are used only 
with Centralized Attendant Service. The signal can be analog or digital. 
Tie trunks are used on calls to or from the following: 
						

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— a Private Branch Exc hange  (PBX)
— an ETN switc h
— an EPSCS or Common Control Switching Arrangement (CCSA) 
office
— MEGACOM Service (AT&T unbanded long distance service.)
nWATS —Provides access to a portion of the DDD network via d e dicated 
trunks to a WATS serving office.  Each WATS trunk terminates as a WATS 
line in the WATS serving office.  The trunks used are always one-way 
outgoing. Outgoing WATS calls to various geographic areas are ma de on 
an attendant-handled basis or a station direct-outward-dial basis. Signals 
can be analo g or digital.
Tie trunks used with the system are administered as either internal or external. 
The internal or external designation controls the type of ringing (which is 
administrable) received at a voice terminal when an incoming tie trunk call 
arrives and controls the routing of the call if it is redirected through the Call 
Coverage feature. The d efault ringing pattern is the following:
nIncoming internal tie trunk calls cause internal-call ringing and will redirect 
according to the redirection criteria administered for internal calls.
nIncoming external tie trunk calls cause external-call ringing and redirect 
according to the redirection criteria administered for external calls.
The number of bursts for internal/external/priority calls is a dministrable in 
G3i-Global and G3V2 and later releases. The Call Coverage feature interaction 
with Tie Trunks is described in detail in Chapter 3 of this manual.
Selection of the trunk group to be used for a given call is determined by digit 
translation on the trunk access code by the AAR/ARS routing tables. Assuming 
an idle trunk in the selecte d group is found, a seizure signal (service request) is 
sent to the distant switch. If the distant switch requires the called number, a start 
dial signal is normally returned to the calling switch, indicating readiness to 
accept digit transmission.
The start dial signal(s) used is dictated by the serving FX office, WATS office, or 
local CO. For interconnection with other private switching systems, the System 
Manager may select the start d ial signal(s) to be used.
‘‘Trunk typ e’’ refers to the physical design of a trunk circuit. Trunk type and the 
start dial signal are often used interchangeably, although trunk type is a more 
accurate term. A brief description of the available trunk types follows:
nGround Start — A ground signal is sent over the trunk ring lead and is 
received over the trunk tip lead.
nLoop Start — A closure signal is sent through the loop formed by the trunk 
leads. 
						

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nImmediate Start — No start dial signals are used. On outgoing  calls, the 
system waits at least 80 milliseconds (a configurable amount of time) after 
sending the seizure signal b efore sending the digits required at the d istant 
switch. This gives the distant switch enough time to attach a digit receiver 
to the call.
nWink Start — A momentary signal (wink) is sent to the distant switc h when 
the trunk is ready to receive digits.
nDelay Dial — A steady signal is sent to the distant switch and is removed 
when the trunk is ready to receive d i gits.
nAutomatic — No dialing is performed. The seizure signal sent or received 
is sufficient to route the call. The call destination is specified when the 
trunk group is administered. The  destination can be the attendant group 
or any extension number assigned in the system.
Trunk groups connecting with a WATS office, FX office, or local CO can be 
ground or loop start. DID trunk groups can be immediate or wink start. Tie trunk 
groups can be delay dial, wink start, immediate start, or automatic.
Trunk groups can be one-way incoming, one-way outgoing, or two-way. Whether 
the trunk group is available for incoming, outgoing, or two-way traffic is called 
direction. A two-way loop-start trunk is subject to glare. Glare occurs when the 
distant switch is trying to use a given trunk for a call to a DEFINITY PBX at the 
same time the DEFINITY system is trying to use the same trunk for a call to the 
distant switch. Incoming calls are not a borted because of glare. The  incoming 
call will complete, and the outgoing call will receive reorder tone (G3i and 
G3vs/G3s). In G3r and G3V2 and later releases, glare retry handling for two-way 
trunks is administrable. Queuing at both ends of a two-way trunk group 
compounds the possibility of glare and is, therefore, not recommended.
Each non-DCS outgoing and two-way trunk group can have a queue. If all trunks 
in the group are busy, the call waits in the queue until a trunk becomes idle. The 
queue length, which is the number of calls waiting, may be from one to 100. A 
queue length of 0 (zero) indicates no queue has been established. This 
information is entered on the trunk group form when the trunk group is 
administered.
Dual Tone Multifrequency (DTMF) (touch-tone) signaling or rotary dial 
(dial-pulse) signaling can be used between switches. The system can send or 
receive either type of signaling required by the distant switch as well as 
ISDN-PRI and R2-MFC and others.
An incoming trunk call to the system can be connected to another trunk, a voice 
terminal, an attendant console, or an announcement. When  the  call  is answered, 
‘‘an answer supervision’’ signal is sent to the distant  public network switching 
office. This signal initiates the recording of the call details normally used for 
charging. Any CO call route d outward is deemed ‘‘answered’’ 10 seconds 
(system d efault; however, this may be administered as higher or lower on the 
trunk group form) after the last d igit is dialed. Tie trunk calls are deemed  
						

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‘‘answered’’ when answer supervision is returned from the far end or when 
answer supervision time-out expires. Also, if there is a trunk incoming from one of 
the previously listed offices on a call of this type, then answer supervision is sent 
to that office. An incoming call to a Direct Department Calling (DDC) or Uniform 
Call Distribution (UCD) recorded delay announcement is deemed ‘‘answered’’ 
when the calling party is connected to the announcement. Other types of 
announcements, such as unassigned number announcements, are treated as an 
unanswered call. 
						

							Functional Description
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System Management
System Management provides the capabilities to control and maintain the system 
and also provides system usage reports to help determine if the system is being 
used as intended. In short, System Management allows the System Manager to 
establish the system, monitor its use, and make additions and/or changes as 
necessary. System management d evices are the Generic 3 Management 
Terminal (G3-MT) or the Generic 3 Management Adjunct (G3-MA). The G3-MA 
system management device is an enhanced PC-based administration system.
!WARNING:
Secure your system from unauthorized access by following the guidelines 
suggested in the GBCS Products Security Hand book, 555-025-600, and in 
the Security  Measures section, Chapter 1.
System Management features and functions are described in this chapter. 
Functions are more fully described in the following documents.
nDEFI NI TY Com munications System Generic 3 V4 Implementation, 
555-230-655
nDEFI NI TY Com munications System Generic 3 V2 Traffic Reports, 
555-230-511
nDEFI NI TY Com munications System Generic 3r Maintenanc e, 555-230-105
Changes made to system translations are effected only at the single system for 
which the changes were made. If a system is part of a network, changes may 
need to be made at more than one system to effect the desired changes to the 
network. Similarly, changes intended for only a single system could affect the 
network. Therefore, the System Manager must understand the effect on the 
network before making any changes.
System Management Features
The following features are associated with System Management:
nAdministration
nAdvice of Charg e
nCall Detail Recording (CDR)
nCustomer-Provid e d Equip ment  (CPE)  Alarm
nFacility Test Calls
nMove Ag ent From CMS
nRecent Change History
nReport Scheduler and System Printer
nSecurity Violation Notification