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Current issue : #8 | Release date : 1986-11-01 | Editor : Taran King
Phrack Inc. IndexTaran King
Phrack Pro-Phile V on TucTaran King
City-Wide CentrexThe Executioner
The Integrated Services Digital NetworkDr. Doom
The Art of Junction Box ModemingMad Hacker 616
Compuserve InfoLotus & Morgoth
Fun with Automatic TellersThe Mentor
Phrack World News VII Part IKnight Lightning
Phrack World News VII Part IIKnight Lightning
Title : City-Wide Centrex
Author : The Executioner
                                ==Phrack Inc.==

                    Volume One, Issue Eight, Phile #3 of 9

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%---%                                       %---%
% P %            The Executioner            % P %
% h %                                       % h %
% a %                and the                % a %
% n %                                       % n %
% t %           PhoneLine Phantoms!         % t %
% o %           -    -    -                 % o %
% m %                                       % m %
% s %    Present: The City Wide Centrex     % s %
%---%                                       %---%

     The CWC (City-Wide Centrex) feature provides multiple location large
business customers with centrex features, attendant features, and dialing
capabilities that are transparent across geographic locations and are
independent of the configuration of the #1AESS switches providing the service.
Historically, centrex customers have been somewhat limited to the bounds of the
servicing switch. Customers could be built across switches, but with
limitations. Multiple locations could be arranged to share some features in
common only when placed in a centrex complex served by a single switch.
Obviously, for this to be feasible, the locations had to be geographically near
each other. The CWC feature expands the concept of the centrex group by
allowing a multi-located business to function as a single centrex arrangement
called a CWC group. Although each customer location remains a part of its own
switch with its own individual capabilities, it now functions as part of the
CWC group. Selected centrex features that were defined to operate within the
bounds of a serving switch centrex group are now redefined to operate within
the bounds of the CWC group. The outer boundary of the CWC cannot exceed the
boundary of the LATA due to LCCIS constraints.

     The CWC feature provides a comprehensive communications package for a
multiple location centrex customer. Some advantages are:

          o Extension to Extension (Intercom) dialing.

          o Concentration of private facilities access at one location.

          o Elimination of dedicated facilities between locations within the
            CWC group.

          o Transparency of feature operation across switches.

Use of CCIS trunks to replace tie trunks results in the need for fewer total
trunks and trunk groups. Remote access reduces the total number of customer
trunks required and centralizes customer facilities at one location. All
switches need LCCIS so that information can be passed between locations.

=Intercom Dialing=

     Intercom dialing gives the customer the ability to dial extension numbers
(intercom) to other locations. This is done either by dialing the interlocation
intercom number or by a speed call code which contains an interlocation
intercom number. The customer has the option of routing these interlocation
intercom calls via simulated private or public facilities. After determining
the intercom number dialed is in location, the originating office routes the
call to that location. The call is identified in the centrex customer's digit
interpreter tables as an interlocation intercom call and normal interoffice
call processing determines routing. A decision is made as to whether simulated
facilities are used for routing the call based on the location identification
of the called line. If needed, a simulated facility is seized. This is
determined by a distant line status request on the called line at the end of
dialing. The originating offices sends information to the terminating office
identifying the call as interlocation intercom call. The CWC group and
location identifier of the calling party are also sent. This is done by using
the RCLDN (retrieval of calling line directory number) to transmit this
information. The terminating office recognizes as incoming call as such. If the
two-way simulated private facilities are used, the count on facilities at the
terminating office is incremented. The use of 2 way simulated pricate
facilities for a call is based on the location identifier of the calling line
and whether simulated private facilities were used on the outgoing side.

=Centrex Attendant Console=

     The tie trunks are replaced by CCIS trunks, therefore some changes are
required in the use of the attendant console. The changes are as follows:

     o Busy Verification and attendant call through tests are not applicable
       since there will no longer be specific trunks dedicated to the customer.

     o The existing trunk group busy lamps are replaced with busy lamps for the
       simulated facilities between locations.

     The digit interpreter table entry at each remote location contains the
"Dial 0" DN for the attendant. This is done to process interlocation intercom
calls which terminate to the attendant. If the attendant console uses a centrex
data link, the line equipment assigned to the DN should specify the call
indicator lamp to be used. A different DN should be used for each location if
separate call indicator lamps are desired for calls from each location. This
call indicator lamp flashes at the intragroup rate of 120ipm (interruptions per
minute) to indicate interlocation intercom calls.
     The RCLDN primitive is used to transmit information for intercom dialing
between locations. In addition, the RDLS priminitive is used to provide CWC
information to obtain the CWC group and location identifier of the called line.
The originating, incoming, and CCIS incoming registers are used to save
information at both he originating and terminating offices. These registers
include the CWC group, CWC location identifier, a CWC call type, and an
indicator whether simulated facilities were used at the originating.

=Remote Access to Private=
=       Facilities       =

     Remote access to private facilities allows the CWC customer to access
physical private trunks and simulated facilities at a single location. This
allows customers to consolidate their private facilities at one location. The
number of trunks required is reduced. Any station can access these facilities
by dialing the same access code as the main location. If a station dials the
access code for a private facility, the call is routed to the main location
using the same facility as an interlocation intercom call. It is then routed
out from the main location. The CWC feature does not allow the customer to use
the ACOF (Attendant Control of facilities) feature from a remote location. The
types of private facilities which are accessible are:

     o Tie Trunks
     o FX (Foreign Exchange)
     o CCSA (Commmon Control switching arrangement)
     o ETS (Electronic Tandem Switching)
     o WATS (Wide Area Telecommunications system)
     o FRS (Flexible Route selection)
     o EEDP (expanded electronic tandem switching dialing plan)

     The CCIS direct signalling messages are used to communicate between the
remote and main locations during the digit collection and analysis of out-going
calls. Once the voice path has been established, a CCIS banded signalling
message transmits the digits collected. A remote access register is used to
store information retrieved during the processing of the signal requests. This
register belongs to the OR (Originating Register) pool at the main location.
     The remote location is responsible for digit collection and transmission
of collected digits. A remote access data CCIS direct signalling message
transmits the digits from the remote to the main location, which returns
instructions for the next action to be performed. The following items are sent
from the remote to the main location:

     o The digits collected.
     o The FRL(facility restriction level) of orig. line.
     o A FRL present indicator
     o A customer changeable speed call indicator.
     o A call forwarding over private facilities indic.
     o An add-on indicator.
     o The CC location identifier of remote location.
     o The remote access register # of the main location.
     o An abandon remote access request indicator.

     The main location analyzes the information transmitted and returns the
next set of instructions to the remote location. The full analysis of a call
may require several direct signalling messages with information saved from the
previous direct signalling messages. This is required to process the current
direct signalling message being saved in the remote register. The information
gathered is used to establish the voice path for the call. Upon receipt of a
direct signalling request, processing is done in accordance with the function
indicated in the remote register. The types are as follows:

     o Translate access code
     o Translate prefix digit
     o "1+" dialing check
     o Check for possible account code
     o Complete account code received
     o 3 digit translation
     o 6 digit translation
     o 10 digit translation
     o Analyze authorization code
     o FRS 3 Digit translation
     o CCSA translation
     o Abandon call

     After processing at the main location is complete, the remote access
register is set up to identify the next type of function. Then, the main
location returns a CCIS remote message to the remote location. The information
returned from the main location is always in the same format and is saved on
the OR.


     The CWC group is allowed many features, here is a list of them.

1. Call Forwarding Variable: Users can forward their calls to remote stations
   located in another office by dialing the access code and the intercom
   number of the CWC station.

2. Call Forwarding Busy Line: Provides for the forwarding of calls to any
   interlocation station within the CWC group upon encountering a busy station.

3. Call Forwarding Don't Answer: Provides for the forwarding of calls that are
   not answered within a predetermined number of ringing cycles.

4. Call Transfer: Allows the station user to transfer any established call to
   any other station within the CWC group with the following constraints.

     o Dropback rules do not permit 2 outgoing trunks to be involved in the
       final 2 party connection. However, 2 outgoing trunks can be involved in
       a 3 way conversation.

     o On interoffice calls involving a fully restricted station, flash
       capability is allowed. However, the controller is not permitted to
       connect the fully-restricted station to any other station, either in
       dropback or a 3 way conversation.

     Cross network call transfer transparency requires that each location be
provided the Call Transfer-Individual or Call Transfer-Individual-All calls
feature. The CTO (call transfer outside) option may be provided.

5. Call Waiting feature provides a burst of tone when the called party is busy
on another call. The types of Call Waiting features and CWC interactions are:

     o Call Waiting Originating: allows a CWC calling station to direct a call
       waiting tone toward a busy station within the same CWC group.

     o Call Waiting Intragroup: gives call waiting tone to a called party
       which has call waiting terminating on all intragroup calls.

     o Dial Call Waiting: Allows originating CWC station users to invoke call
       waiting on CWC intragroup calls by dialing an access code followed by
       the extension number of the station to be call waited.

6. Distinctive Ringing/CW Tone: Allows a CWC station user to determine the
source of a call incoming to the station. This is done by associating a
distinctive ringing or tone pattern with the incoming call based on its source.
Interlocation CWC calls receive intragroup treatment.

7. Message Desk Service: Provides centralized and personalized call coverage or
message answering capabilities which can serve the needs of all CWC locations.
The Call Forwarding Variable and Call Forwarding Busy Line/Don't Answer feature
are needed of forwarding calls from stations within the CWC group.

8. LASS (Local Area Signalling Service): Provides the called party with call
management and security services. Local CCIS is required for multiple-office
grouping within a LATA for intercom calls. The following features comprise the
LASS offering :

     o Automatic Recall: Enables a station user to place a call to the LCDN
       (Last Call Directory Number) currently associated with the users fone.
       The LCDN can either be the last party called by the station user or the
       last party to call the station user.

     o Distinctive Alerting: Allows the station user to prespecify a set of
       numbers which activate a distinctive ring or distinctive call waiting
       tone. The CWC extension numbers can be entered on the screen list. When
       the user receives a call from one of these numbers, the phone if idle,
       will ring with a special distinctive ringing pattern. If a call waiting
       customer's line is busy, a special tone notifies the customer of the
       impending call.

     o ICLID: provides the number which is calling the station user. (Explained
       in other files)

     o Selective Call Forwarding: (Explained in other file)

     o Selective Call Rejection: Provides the user with the capability of not
       being alerted by calls from a specified set of numbers. The user inputs
       the numbers to be rejected from the station set. These numbers are
       specified either directly (dialed in) or as the number of the last call
       received. The CWC extensions are allowed on the screen list.

=(C) 1986 The Executioner and The Egyptian Lover and PLP  =
This file is based on the AT&T document for the CWC.
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