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229 lines
11 KiB
Text
229 lines
11 KiB
Text
==Phrack Inc.==
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Volume Two, Issue Ten, Phile #5 of 9
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^ ^
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[<+>] [<+>]
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/|-|\ /|-|\
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\|P|/>/>/>/>/>/>/>/>/>PLP<\<\<\<\<\<\<\<\<\|P|/
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|h| ^ ^ |h|
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|a| ]+[The Executioner]+[ |a|
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|n| |n|
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|t| Call Phreak Klass, Room 2600 |t|
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|o| [806][799][0016] |o|
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|m| |m|
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|s| [Circuit Switched Digital Capability] |s|
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|-| ----------------------------------- |-|
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|S| |S|
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|e| Part I of II in this series of files |e|
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|x| |x|
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|y| Written for PHRACK, Issue 10. |y|
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/|-|\ /|-|\
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\|$|/>/>/>/>/>/>/>/>/>PLP<\<\<\<\<\<\<\<\<\|$|/
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[<+>] [<+>]
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========
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=Part I=
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========
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The Circuit Switch Digital Capability (CSDC) allows for the end to end digital
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transmission of 56 kilobits per second (kb/s) data and, alternately, the
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transmission of analog voice signals on a circuit switched basis.
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=====================
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=Network Perspective=
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=====================
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The CSDC feature was formerly known as PSDC (Public Switched Digital
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Capability). These two terms can be used synonymously. The CSDC feature
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provides an alternate voice/data capability. If a SLC Carrier System 96 is
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used, digital signals are transmitted by T1 signal. If the loop is a two wire
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loop, the CSDC feature utilizes time compression multi-plexing (TCM) which
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allows for the transmission of digital signals over a common path using a
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separate time interval for each direction. During a CSDC call an end user may
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alternate between the voice and data modes as many times as desired. The CSDC
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feature can support sub-variable data rates from customer premises equipment,
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but a 56 kb/s rate is utilized in the network. Some possible applications of
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the CSDC feature are:
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1. Audiographic Teleconferencing.
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2. Secure Voice.
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3. Facsimile.
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4. Bulk Data.
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5. Slow scan television.
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The ESS switch provides end user access and performs signalling, switching,
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and trunking functions between the serving ESS switch and other CSDC offices.
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End users of CSDC require a network channel terminating equipment circuit
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(NCTE) which is the SD-3C476 or its equivalent. End user access is over 2-wire
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metallic loops terminating at the metallic facility terminal (MFT) or SLC
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Carrier System. End users not served directly by a direct CSDC ESS office, can
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access CSDC equipment through a RX (Remote Exchange) access arrangement via
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use of a D4 Carrier System and if required, a SLC Carrier System. The
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T-Carrier trunks serve for short haul transmissions while long haul
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transmissions are served by digital microwave radio and other digital systems.
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If the NCTE interface is used with customer premises equipment, a miniature
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8-position series jack is used to connect the NCTE to other equipment. The
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jack pins are paired off; data transmit pair, data receive pair, a voice pair,
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and a mode switch pair. The data pairs support the simultaneous transmission
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and reception of digital data in a bipolar format at 56 kb/s. The data pairs
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also provide for the xmission of control information to and from the network.
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The voice pairs supports analog signal transmission and provides for call
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setup, disconnect and ringing functions. The mode control pair provides
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signals to the network when a change in mode (voice to data/data to voice) is
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requested by the customer.
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A CSDC call is originated over a 2-wire loop which can also be used for
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Message Telecommunication Service (MTS) calls. Lines may be marked (MTS/CSDC
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or CSDC only). Touch tone is needed to originate a CSDC call. Originations may
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be initiated manually or with Automatic Calling Equipment (ACE) if available.
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Digit reception, transmission and signalling follow the same procedures used
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for a MTS outgoing call on CCIS or non-CCIS trunks. However CSDC calls are
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ALWAYS routed over digital transmission facilities.
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The long term plan also allows for EA-MF (Equal Access-Multi Frequency)
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signalling and improved automatic message accounting (AMA) records. A CSDC
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call is screened to ensure that the originating party has CSDC service and
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that the carrier to be used provides 56 kb/s voice/data capability. A blocked
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call is routed to a special service error announcement. Non-CSDC calls are not
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allowed to route over CSDC-only carriers. Non-payer screening is not allowed
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for CSDC calls using CCIS signalling.
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A CSDC call is routed directed to the carrier or indirectly via the Access
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Tandem (AT) or Signal Conversion Point (SCP). The call is terminated directly
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from the carrier to the end office or indirectly via the AT or SCP. Signalling
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for direct routing is either CCIS or EA-MF and is assigned on a trunk group
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basis.
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The AT is an ESS switch which allows access to carriers from an end office
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without requiring direct trunks. Signalling between end offices and the AT is
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either EA-MF or CCIS. Trunks groups using EA-MF signalling can have combined
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carrier traffic. Separate trunk groups for each carrier are required for CCIS
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signalling.
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The SCP is an ESS switch which allows access to carriers using only CCIS
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signalling from offices without the CCIS capability. Separate trunk groups for
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each carrier are used between the originating end office and the SCP. Separate
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trunk groups are optional between the SCP and the terminating end office and
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the terminating end office. Signalling between the end office and the SCP is
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MF. The SCP must have direct connection to the carrier using CCIS signalling.
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=========================
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=Remote Switching System=
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=========================
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The RSS can be used as a remote access point for CSDC. The compatibility of
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RSS and CSDC improves the marketability of both features. The RSS design
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allows a provision for the support of D4 special service channel bank
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plug-ins. This provision allows for such applications as off premises
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extensions, foreign exchanges lines, and private lines. Thus the RSS can be
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used as a CSDC access point in a configuration similar to the CSDC RX
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arrangement.
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================
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=Centrex/ESSX-1=
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================
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The CSDC feature is optionally available to Centrex/ESSX-1 customers. Most of
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the capabilities of Centrex service can be applied to Centrex lines that have
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been assigned the CSDC feature. In voice mode, the Centrex/CSDC line can
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exercise any of the Centrex group features that have been assigned to the
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line. In the voice/data mode, several Centrex features are inoperable or
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operate only on certain calls. The CSDC feature can be provided for a Centrex
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group as follows:
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1. Message Network Basis (MTS)
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2. IntraCentrex group basis
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3. InterCentrex group basis
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4. Any combination of the above
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===============================
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=User Perspective for the CSDC=
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===============================
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To establish a CSDC call, a CSDC user goes off hook, receives dial tone and
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dials. The dialing format for the CSDC/MTS is as follows for interim plan:
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#99 AB (1+) 7 or 10 digits (#)
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The customer dials '#99' to access the CSDC feature. The 'AB' digits are the
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carrier designation code. No dial tone is returned after the 'AB' digits. The
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1+ prior to the 7 or 10 digit directory number must be used if it is required
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for MTS calls. The '#' at the end is optional, if it is not dialed, end of
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dialing is signalled by a time-out.
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The long term dialing format for the CSDC/MTS is as follows:
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#56 (10XXX) (1+) 7 or 10 digits (#)
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Dialing '#56' indicates 56kb/s alternate voice/data transmission. the '10XXX'
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identifies the carrier to be used for the call. If '10XXX' is not dialed on an
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inter-LATA call, the primary carrier of the subscriber is used. If '10XXX' is
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not dialed on an intra-LATA call, the telco handles the call. The long term
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plan also allows for several abbreviated forms. Dialing '#56 10XXX #' is
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allowed for routing a call which prompts the customer to dial according to the
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carrier dialing plan. Dialing '#56 10XXX' followed by a speed call is also
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allowed. If a customer has pre-subscribed to a carrier which can carry CSDC
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calls and the CSDC access code is stored as part of the speed calling number,
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the customer dials the speed calling code to make a CSDC call.
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Regular ringing is applied to the called line and audible ringing is applied
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to the calling terminal. Once the voice connection is established, either
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party can initiate the switch to data mode, if desired. To initiate a change
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in mode a CSDC user must initiate a mode switch command via a closure of the NCT
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An example of a mode switch:
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Suppose party A wants to switch to data. Party A issues a mode switch
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command and receives a signal called far end voice (FEV) which is a bipolar
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sequence (2031 hz at 60 ipm). Party A may now hang up the handset at any time
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after initiating the mode switch command. Party B receives a far end data
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(FED) tone (2031 Hz at 39 ipm) indicating party A wants to switch to data. If
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party B agrees to switch to data, party B must initiate a mode switch command.
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Party B may nor hang up the handset. Data transmission is now possible.
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To switch to the voice mode, anyone can initiate it. To switch, party A
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would pick up the handset and initiate a mode switch command and will receive
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the FED tone. Party B receives the FEV tone indicating that party A wants to
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go voice. Party B must now pick up the hand set and initiate a mode switch
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command. To terminate a call, either party may just leave the handset on and
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indicate a mode switch. If termination is issued during a mode conflict, time
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out will disconnect the call, usually about 10 or 11 seconds.
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Centrex/ESSX-1 customers may utilize the CSDC service in several ways if they
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have CSDC terminals with the necessary on premises equipment. The standard
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CSDC call is initiated by dialing the message network access code, (9). The
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dialing sequence is then identical to the plan for MTS:
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#99 AB (1+) 7 or 10 digits (interim plan)
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#56 (10XXX) (1+) 7 or 10 digits (#) (long term plan)
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The dialing pattern to establish interCentrex or intraCentrex CSDC calls is as
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follows:
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CSDC access code + extension
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An intraCentrex/CSDC call is initiated by dialing the trunk access code
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assigned to route a loop-around Centrex/CSDC trunk group. Next, the extension
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of the desired station is dialed. To establish an interCentrex call a
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different trunk access code must be used to route the CSDC calls to another
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Centrex group instead of a station.
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The CSDC maintenance circuit has a dialable digital loopback. This loopback is
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very useful in CSDC testing. A customer can check their access line by dialing
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the test DN. The loop is automatically activated when the call is answered.
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================
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=End of Part I.=
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================
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Part II: The CSDC hardware, and office data structures.
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=======================================================
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= (c) 1986 The Executioner and The PhoneLine Phantoms =
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=======================================================
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