ATT System 25 Reference Manual

							Transfer To Data
Data Call Preindication
A multiline voice terminal user, by going off-hook and pressing an idle DATA button, may
indicate that a data call will be attempted. This reserves the associated data port and a
modem pool conversion resource.This procedure is recommended when the data call is a
trunk call. The data port reservation is acknowledged by a winking status LED at the DATA
button. Subsequently, invoking Transfer To Data transfers the call to the associated data
terminal.
Preindication is canceled:
l If the user goes on-hook before transferring the call to data
l If the user preindicates on a second DATA button
l If, after dialing is complete, a second DATA button is pressed. Preindication is
canceled for the first data terminal and the data call is transferred to the second data
terminal.
When Preindication is canceled, the associated pooled modem conversion resource
reservation is canceled.
Interactions
The following feature interacts with Transfer To Data.
Modern Pooling: If a conversion resource is required on an external call, invoking Data Call
Preindication will cause a pooled modem conversion resource to be reserved. If none is
available (e.g., the system has no Pooled Modem CP), Reorder Tone is provided. (This will
occur whether a conversion resource is actually required or not.)
Administration Requirements
Voice Terminal Port:
l Assign DATA button
2-345 
						

							FEATURES AND SERVICES
Trunk Groups
Description
This feature allows each trunk in the system to be assigned to one of up to 16 trunk groups.
Trunks link two switching systems, such as System 25 and the local CO or System 25 and
another PBX. Although not required,trunks can be grouped together in trunk groups
(sometimes referred to as pooled facilities) when all the trunks in the group perform the
same function. This grouping provides resource pooling that results in better service with a
given number of trunks.It also simplifies administration and calling. Calls are routed to the
appropriate trunk group; an idle trunk, if available, is selected from the group. Up to 16 trunk
groups (pooled facilities) may be assigned in the system.
Several different kinds of trunk groups can be assigned in System 25:
l Central Office (CO)—Provides a link with the local CO for calls except Direct Inward
Dial (DID) calls. Trunks classed as “CO” have a number of special characteristics.
l Foreign Exchange (FX)—CO trunks that connect to a CO other than the local CO.
l Wide Area Telecommunications Service (WATS)—CO trunks that connect to an
Outward WATS office or a dial 800 (in-WATS) Service office.
l Direct Inward Dial (DID)—Provides incoming (only) service from the local CO. These
calls go directly to voice terminals instead of through the attendant.
l Tie—Provides a link with another private switching system or network.
Trunk groups can be one-way (incoming) or two-way.Selection of the trunk group to be
used for a given call is determined by the initial digits of a dialed number (or by the ARS
feature). These digits are referred to as the facility access code. Each trunk group is
assigned a unique code.Assuming an idle trunk in the selected group is found, a seizure
signal (service request) is sent to the distant switch.If the distant switch requires dialed
digits (as all but some tie trunks do), a signal (Dial Tone) is returned to System 25, indicating
readiness to accept dialed digits.
Trunk type refers to the physical design of a trunk circuit.The trunk types supported and a
brief description of each are given below.Refer to Section 3, “Functional Description” and
Section 9, “Glossary” for additional information.
l Loop Start—A closure signal is sent through the loop formed by the trunk leads.
l Ground Start—Similar to loop start but enhanced with ground signals.
l Immediate Start—No start dial signals are used. On outgoing calls, the system waits
at least 80 ms after sending the seizure signal before sending the digits required by
the distant switch.This allows the distant switch enough time to attach a digit
receiver to the trunk (Tie and DID trunks).
2-346 
						

							Trunk Groups
l Wink Start—A momentary signal (wink) is sent
trunks).
l Delay Dial—A steady signal is sent to the distant
to receive digits (Tie trunks only).to the distant switch (Tie and DID
switch and is removed when ready
l Automatic—No start dial signals are used.
The seizure signal sent or received is
sufficient to route the call (Tie trunks only).
Trunk groups connecting with a local CO, WATS office, or FX office can be ground or loop
start. DID trunk groups can be immediate or wink start. Tie trunks groups can be automatic,
wink start, immediate start, or delay dial.
Dual Tone Multifrequency (DTMF) signaling (touch-tone) or dial pulse signaling can be used
between the System 25 and the far end switch. System 25 can send or receive either type of
signaling required by the distant switch (DID trunks can only receive dial pulse signals). The
type to be used is specified when the associated trunk is administered.
An incoming call can be connected to another trunk, a voice terminal, a data endpoint, an
attendant console, or an announcement. When the call is answered, an off-hook indication is
sent to the serving office.This signal may be used to initiate the recording of call details
normally used for billing.
Trunks in a two-way trunk group should be translated (at the SAT) in the same order that the
serving office hunts when searching for an idle trunk.System 25 will then hunt in reverse
order. This reduces the probability that both switches will attempt to seize the same trunk at
the same time.
Considerations
Trunks of the same type and Class Of Service may be assigned a (Pooled) Facility Access
Code. This provides users with dial or direct (button) access to the trunk pool. Trunks may
be dial access restricted to reserve them for ARS and direct access only.
Refer to “Recommended Central Office Trunk Facilities” (Section 5) for an estimate of CO
trunk requirements based on traffic considerations. See the “Pooled Facility-Direct Access”
and “Pooled Facility-Dial Access” feature descriptions for additional information.
Trunks may be reserved for incoming calls (e.g., sales or service department calls) by
specifying this in the (administered) Class of Service code.
Interactions
The following features interact with Trunk Groups.
Direct Group Calling:Most trunks may be administered so that incoming calls are directed
to a specified DGC group. For tie trunks, only the automatic-in type may be so administered.
2-347 
						

							FEATURES AND SERVICES
Facility Access Restriction (see “Calling Restrictions”):Stations may be restricted from
dialing the CO trunk pool and/or all (fifteen) other trunk groups (as a whole). Stations so
restricted may still dial out if they are transferred to a trunk by another station not so
restricted.
Tie Trunks: Refer to the “Tie Trunks” feature description.
Toll Restriction (see “Calling Restrictions”): When toll restricted stations access FX, WATS,
or Tie trunks, they are not toll restricted (i.e., toll restriction applies to CO trunks only).
Administration Requirements
Trunk Port:
l Assign Trunk Type And Number.
l Assign Class Of Service Code (DID: 1-4; Other: 0-15).
l Assign Facility Access Code; default codes are based on the CPs in a system. They
are assigned as follows:
Loop Start Trunks - 100.
Ground Start Trunks - 101.
Tie Trunks - 102.
l Allow Dial Access (yes or no; default = yes).
l Assign To DGC Group (Group Number 1-32, or 0 for none; default = 0).
l Make This a Directed Night Service Trunk (yes or no; default = yes).
l Assign Night Service Delay Announcement (Announcement 1 or 2 or 0 for none;
default = 0).
l Dial-Inward Capability (Tone or Pulse; default = Pulse [Tie trunks only]).
Hardware Requirements
Associated trunk port interfaces.
2-348 
						

							Trunk-To-Trunk Transfer
Trunk-To-Trunk Transfer
Description
This feature allows users to connect incoming trunk calls to other outside trunks and then
hang up (under certain conditions).
Incoming trunk calls may be transferred to another trunk, or conferenced with another trunk.
In all cases and at all times, either a System 25 station must remain in the conference or one
of the calls must be an incoming call on a ground start, loop start (administered for trunk-to-
trunk transfer), DID, or tie trunk.The other call may be on any type of trunk and may be
incoming or outgoing.
Considerations
Trunk-to-trunk transfer is particularly useful when an outside caller requests a transfer to
another outside number.For example, an employee can call in and have their call
transferred elsewhere. Note that as long as an inside station stays on the call (even if a
multiline station puts the call on hold and hangs up) any two trunks may be conferenced. If
the station drops out of the call, the trunk conference will be torn down unless the above
conditions are met.
If a System 25 station enters a trunk-to-trunk transfer call via a line appearance button for
one of the conference trunks, the call will still be broken down when one of the outside
parties hangs up.
A Direct Group Calling call that comes in on a ground start trunk and is answered at a
single-line set is not eligible for trunk-to-trunk transfer.
Interactions
The following feature interacts with Trunk-To-Transfer Transfer.
Conference: Trunk-To-Trunk transfers may be set up using the Conference feature. The
conference must include an incoming trunk call on either a ground start, DID, or tie trunk if it
is to continue after all inside stations have dropped off.
Administration Requirements
System:
l Allow trunk-to-trunk transfer on loop start trunks? (yes or no; default = no).
This capability should be assigned only where Central Offices give a reliable
disconnect signal of at least 600 milliseconds at the end of the Loop Start call.
2-349 
						

							FEATURES AND SERVICES
User Changeable Options
Description
User Changeable Options allows a data terminal user who is in the Command Mode to view
and change the settings of certain data port options.This feature is available to users of
Data Line CP ports; users of STARLAN Interface CP ports cannot change their port options.
Table 2-L contains brief descriptions of the user changeable options.
Table 2-L.User Changeable Options
OptionDefinition
Speedlow, 300, 1200, 2400, 4800, 9600, 19200, autobaud
Parityodd, even
Permit MismatchAllows two data endpoints to communicate at
different rates.
Local EchoDetermines whether characters from the data
equipment will be echoed by System 25 during
Command Mode.
Answer TextEnables call progress messages to be displayed
at the called data endpoint.
Connection IndicationDetermines whether users who have Command
Mode enabled will receive the “CONNECTED”
message when a connection has been made.
Recall SequenceTwo short breaks or one long break; the sequence
(disconnect)used to disconnect a data call.
Note:The System Administrator may,under data port administration, deny
permission for users of specific data ports to self-administer these options.
The user selects the Options menu from the Command Mode entry level menu. (Figure 2-62
illustrates all available Command Mode menus.) The user now has the choice of viewing
options, changing options, or exiting the Options menu.
2-350 
						

							User Changeable Options
2-351 
						

							FEATURES AND SERVICES
Viewing Options
When  is selected, current and default values for the various data port
options are displayed, as shown below:
OPTIONSCURRENTDEFAULT
At this point theSpeed (highest)
960019200 (Auto)
Parity
EvenEven
MismatchYesNo
Local EchoYesYes
Answer TextYesYes
Connect Indicat.YesYes
Recall SequenceBr-BrBr-Br

user can exit from the View options menu, Change options, or View options
again (redisplays the Options table).If the user elects to exit, the terminal returns to the
Command Mode entry level menu.
Note:Typing the capital letter found within a menu will select that item and move
the user up or down the menu tree.For example, the user simply enters X or
x (lower-case) to  the Options menu shown above and return to the
entry level menu.
Changing Options—General
When on the Options Menu, the user selects 
(with the space bar) beneath  and pressing
single letter code (c) associated with that item.either by moving the cursor
RETURN, or by typing the
If the user selects  from the Options menu, the first half of the Change
Options menu is displayed, as shown below and on Figure 2-62.


< local Echo>
If the user selects , the second half of the Change Options menu is displayed:


lf the user selects  from the second half of the menu, the first half of the Change
Options menu is redisplayed. In this way, users can“toggle” back and forth between the
first and second halves of this menu.
Since these two lines are actually two halves of a single menu, users may select a particular
menu item while active on either half of the menu. For example, users who are active on the
first half of the menu may select  by typing “a”.
2-352 
						

							User Changeable Options
Once a user has selected an option to be changed, a menu of valid settings for this option is
displayed (, , etc.).An “X” is displayed beneath the current setting of the
options, or beneath an option that may have been changed but not yet enabled. For all
options except  (see below), settings may be selected either by moving the cursor
(using the space bar) beneath the item desired and then pressing RETURN, or by typing the
single-letter code associated with that setting.The user is then returned to the Change
Options menu to make additional changes if required.
Changing Data Port Speed
The procedure for changing Speed settings is different from the procedure for changing the
settings of other options.Within the Speed menu, the user may find that several values are
marked with Xs. To change a speed, move the cursor beneath each value to be changed
and type “+” to add the value or“-” to delete it. Once the new settings have been marked,
press RETURN to translate the plus and minus signs to their proper “X” values and then
type “x” to  from the Speed menu and return to the Change Options menu. For
example:
The user enters the Speed menu and finds the following settings active:



X
XXXX
To remove 9600 baud and activate autobaud, enter - under  and + under , as
shown below:



XX
XXX-+
With the cursor under any item except , pressing RETURN provides the following:



XXXXX
Entering “x”now allows the user to  the Speed menu and return to the Change
Options menu.The user can make additional changes, as required.
When all of the changes have been made, the user should  the Change options
menu. The following menu is then displayed:

From the above menu:
l If the user selects , the user is returned to the Command Mode entry level
menu, deleting any option-change requests.
l If the user selects , the Change Options menu is displayed and
the user can make additional changes as required.
2-353 
						

							FEATURES AND SERVICES
l If the user selects, the following menu is displayed:
OPTIONSCURRENTREQUESTED
Speed (highest)96004800 (Auto)
ParityEvenEven
MismatchYesYes
Local EchoYesYes
Answer TextYesYes
Connect Indicat.YesYes
Recall SequenceBr-BrBr-Br
The value in the CURRENT column indicates the current (active) status of the option.
The value in the REQUESTED column indicates the most recently entered value (not
yet enabled).
l If the user selects ,the system incorporates the changes
requested and displays the message DISCONNECTED. If Autobaud is off, the user
must now press BREAK to return to Command Mode. If Autobaud is on, the user
must press BREAK and RETURN to return to Command Mode.
Note:If a user attempts to enable options during a “SAVE” operation by the
system administrator, the message “options changed FAILED” will be
displayed. The user will be returned to the top level of the Command Mode
menu, and all change requests discarded. After waiting a few minutes, the
user may try again to change his/her data port parameters.
Considerations
For those cases where a
option changes,
the data port to
change.
Interactions
the Userdata terminal user accesses various data endpoints, each requiring
Changeable Options feature simplifies the process of administering
allow data call-setup. A system administrator is not required to enter each
The following feature interacts with User Changeable Options.
Expert Mode: See the Expert Mode feature description for an abbreviated method of
accessing Command Mode menus.
2-354