ATT System 25 Installation And Maintenance Manual

GLOSSARY
FacilityBy technical type these include loop-start, ground-start, DID, data,
and automatic ringdown trunks. These facilities may be accessed by
their facility access codes (FACS).
Restriction Level (FRL)
A restriction parameter associated with the Automatic Route
Selection (ARS) feature.Determines whether a particular station can
access a particular trunk.
Fast Busy Tone
Feature
Feature
Foreign
Foreign
ForeignSee Reorder Tone.
A specifically defined function or service provided by the system....

GLOSSARY
Ground-Start Trunk
On outgoing calls, System 25 transmits a request for service to the
distant switching system by grounding the trunk ring lead. When the
distant system is ready to receive the digits of the called number,
that system grounds the trunk tip lead. When System 25 detects this
ground, it removes the ground from the ring lead and the trunk is
ready for service.
Home Numbering Plan Area (HNPA) Code
The local area code. Does not have to be dialed to place calls to
numbers within the...

Loop-Start Trunk
Modem
ModemSimplest type of central office (CO) trunk. Calls are originated by
providing a dc path between the tip and ring leads. The CO detects
the loop current thus drawn and returns dial tone. Incoming calls are
signaled by the CO placing an ac ringing voltage between the tip and
ring leads. (The port circuit pack detects this signal.)
A device that modulates and demodulates signals transmitted over a
communications path. Used to connect Data Terminal Equipment to
the system’s analog...

GLOSSARY
Number Plan Area (NPA)
The area code.
Off-Premises Station (OPS)
An arrangement provided by the local telephone company permitting
remote terminal equipment to operate as though it were directly
connected to the system.This tariffed service can be provided only
for FCC-registered single-line voice terminals.
Out-of-Building Station
Terminal equipment directly connected to the system, but not located
in the same buildingas the common equipment.Special
arrangements are made to protect the system...

GLOSSARY
l Floating—Assigned to visitors who will be moving about the
premises.Floating PDCs may be associated with the
attendant position or may be “logged in” by the user at any
voice terminal. Calls to the floating PDC will ring at the
terminal where “logged in. ”
Pickup Group
A group of individuals who can answer any incoming call within the
group by dialing a code.
Port
An interface circuit between System 25 and associated trunks and
terminals. Specifically:
l Terminal port (station port)
l Facility...

Protocol
A set of conventions or rules governing the format and timing of
message exchanges to
errors.
Public Network
The network that can be
or long-distance calling.
Queuecontrol data movement and correction of
openly accessed by all customers for local
An ordered sequence of tasks to be processed.
Queuing
.The process of holding calls in order of their arrival to await
connection to an attendant, to a DGC group, or to an outgoing trunk.
Calls are automatically connected in first-in, first-out...

GLOSSARY
Reorder Tone
Atone repeated 120 times a minute; indicates that at least one of the
facilities, such as a trunk or a digit transmitter, required for the call is
not available. Also called Fast Busy Tone.
Single-Line Voice Terminals
Single-line voice terminals served by a Tip Ring Line or Analog Line
circuit pack (2500 series and 7101 A voice terminals or industry
standard Dual-Tone  Multifrequency equivalent).
Software
A set of computer programs that accomplishes one or more tasks.
Station
A...

GLOSSARY
Switch
The software-controlled communications processor complex that
interprets dialing pulses/tones/keyboard characters and makes the
proper interconnections both within the system and outside the
system. The switch itself consists of a digital computer, software,
storage device (memory), and associated circuit packs
hardware necessary to perform the actual connections.
Switchhook
and special
The button(s) on a voice terminal located under the receiver. A user
typically goes “off-hook” to place...

GLOSSARY
Terminal Equipment
Equipment used to change information (sound, keystrokes) into an
electrical signal compatible with System 25’s port circuits. (Voice
and data terminals are the two primary types.)
Tie Trunk
A telecommunications channel that directly connects two private
switching systems.
Time-Division Multiplex Bus
A special bus that is time-shared by preallocating short time slots to
each transmitter on a regular basis. In a PBX, all port circuits are
connected to the time-division multiplex...

GLOSSARY
Trunk Group
Telecommunications channels assigned as a group for certain
Trunk Port
The hardware (circuit pack) providing an interface between the
system and central office (CO)/network trunks.
Unit Load
A measurement used to evaluate a System 25 cabinet’s power load
capacity. Each System 25 cabinet can handle 80 unit loads of 48-
volt power. One unit load equals 44 mA.
Voice Terminal
A single-line or multiline voice instrument (that is, telephone). See
Terminal Equipment.
Wide Area...