ATT System 25 Reference Manual

							GLOSSARY
Data Endpoint
Two general groups: those having a DTE-type interface, which encompasses almost all of
the data terminal devices; and the group of DCE interface devices which are primarily
modems. However, it must be noted that within each category, control interfaces may also
vary. Refer to Analog Data Endpoint and Digital Data Endpoints for additional information.
Data Module
A data interface device (i.e.,Asynchronous Data Unit) providing a standard interface
between customer-provided data equipment and a data port on the switch.
Data Terminal Equipment (DTE)
DTE refers to a specific RS-232C connector termination designed to connect directly to a
DCE-type connection. Typically associated with video display terminals, printers, and
computers which either originate or terminate a data transmission path.
Data Terminals
Refers to RS-232C-compatible Data Terminal Equipment.
Delay-Dial Tie Trunk
After a request for service (called a seizure) is detected on an incoming trunk, the system
sends a momentary signal followed by a steady tone over the trunk. This informs the calling
party that dialing can start. This type of trunk allows dialing directly into the system. That is,
the digits are received as they are dialed.
Digital Data Endpoints
In System 25, digital data endpoints include any digital device providing an RS-232C
connection interface to the switch. The connection is via Asynchronous Data Units (ADUs)
to the switch.
Direct Extension Selector (DXS) Console
An option at the attendant console that allows an attendant direct access to voice terminals
by pressing a Group Select button and a DXS button.
EIA: (Electronics Industries Association)
ESF
Extended Super Frame (ESF) is the successor to D4 framing.
Emergency Transfer Unit
Provides direct connection of designated Power Failure Transfer (PFT) registered voice
terminals to the CO during a power failure or other service interruption.
Equal Access
Provides access to any Interexchange Carrier (IXC).
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							GLOSSARY
Equalization
The DS1 signal is shaped so that when it reaches the cable-end it conforms to the
DSX-1 interface power specification.
Erlang
A traffic measuring unit that expresses the load of one or more traffic-handling
devices [36 CCS equals 1 erlang - see CCS (Hundred Call Seconds)].
Extension Number
One- through four-digit number assigned to each voice terminal and data end point in
the system.Also see “Personal Dial Code”
Extended Station
A single-line voice terminal located more than 2000 feet from the system cabinets.
External Call
A connection between a system user and a party on the public telephone network or
on a tie trunk; usually referred to as an outside or trunk call.
FRL: (Facility Restriction Level)
Facility (physical)
A transmission channel to another switching system; to a Central Office for example.
By application, examples are:
l CO Trunks
l FX Trunks
l WATS Trunks
l Tie Trunks
By technical type these include loop start, ground start, DID, automatic ringdown, etc.
These facilities may be accessed by their facility access codes (FACs).
Feature
A specifically defined function or service provided by the system.
Feature Button
A labeled button on a voice terminal or attendant console designating a specific
feature.
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							GLOSSARY
Foreign Exchange (FX)
A central office other than the one providing local access to the public telephone
network.
Foreign Exchange Trunk
A telecommunications channel that directly connects the system to a central office
other than its local central office.
Foreign Numbering Plan Area Code (FNPA)
Frame
An area code other than the local area code; also known as the “other area code.”
The foreign area code must be dialed to call outside the local geographical area.
Slip
A slip is the deletion or repetition of a frame. Slips are caused by differences in clock
frequencies. Generally, a slip involving the synchronization will result in most or all
spans experiencing misframes. Slips are not caused by noise on the transmission
line.
Framing
Framing is the process of segmenting and identifying the information carried on a
digital facility.
Ground-Start Trunk
On outgoing calls, System 25 transmits a request for services 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 the
System 25 detects this ground,the digits are sent. (Tip and ring are common
nomenclature to differentiate between ground-start trunk leads.) On incoming calls,
detection of ground on the tip lead is sufficient to cause the call to route to a
predetermined destination,normally the system attendant group. No digits are
received.
HFAI: (Hands-Free Answer on Intercom)
Home Numbering Plan Area Code (HNPA)
The local area code; also known as the “home area code.” The local area code does
not have to be dialed to call numbers within the local geographical area.
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							GLOSSARY
Immediate-Start Tie Trunk
After establishing a connection with the distant switching system for an outgoing call, the
system waits a nominal 65 milliseconds before sending the digits of the called number. This
allows time for the distant system to prepare to receive the digits. Similarly, on an incoming
call, the system has less than 65 milliseconds to prepare to receive the digits.
Inside Call
A connection between two parties within the system.
Intercept Tone
An alternating high and low tone; indicates a dialing error or denial of the service
requested.
Interchangeable Numbering Plan Area (INPA)
Allows interchangeable central office and area codes.
Interface
A common boundary between two systems or pieces of equipment.
Internal Call
A connection between two users within the system. Same as an inside call.
I-Use LED
A red LED on a multiline voice terminal that lights to show which call appearance will be
selected when the handset is lilted or which call appearance is active when a user is off-
hook.
LDN: (Listed Directory Number)
LED: (Light Emitting Diode)
LMA (Loss of Multiframe Alarm)
Loss of Multiframe Alarm applies only to Common Channel signaling and indicates the near
end is unable to synchronize to the multiframe pattern received in the 24th DS0 channel.
LOS (Loss of Signal Alarm)
LOS alarm occurs when the pulse density on the DS1 falls below the level where clock can
be derived from the bit stream.
November 19959-9 
						

							GLOSSARY
Loop Start Trunk
After establishing a connection with the distant switching system for an outgoing call,
System 25 waits for a short period of time before sending the digits of the called number.
On incoming calls, the received request for service is sufficient to cause the call to route to
a predetermined destination, normally the system attendant group. No digits are received.
MET: (Multibutton Electronic Telephone)
Misframe
Frame in which framing bits where observed to be in error.
Modem
A device that modulates and demodulates signals transmitted over a communications path.
Used to connect Data Terminal Equipment to the system’s analog ports. The system
provides a pooled modem conversion resource(12 resources maximum per system—212A
compatible).
Modem Pooling
Provides shared-use conversion resources that eliminate the need for a dedicated modem
when an analog data end point accesses, or is accessed by, an analog line or trunk.
Multiline Voice Terminal
A terminal equipped with several call appearance buttons for the same extension number.
Allows the user to handle more than one call, on that same extension number, at the same
time.
Multiplexed
The simultaneous transmission of two or more signals over a common transmission
medium.
NPA: (Number Plan Area)
NANP: (North American Numbering Plan)
Network
An arrangement of inter- and/or intra-location circuits designed to perform specific
functions.
Network Interface
Provided by the CO telephone company in two forms: (1) RJ21X for trunk facilities other
than tie trunks. (2) RJ2GX for tie trunk facilities.
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							GLOSSARY
Off-Premises Station (OPS)
Ones
An arrangement provided by the local telephone company which permits remote
Terminal Equipment to operate as though it was directly connected to the System 25.
This tariffed service can only be provided for FCC registered single-line voice
terminals.
Density
In synchronous communications systems where clocking is embedded in the data
stream, a required number of signal transitions must occur in order to accurately
recreate the clock at the far end. In the T1 carrier system, this is known as the ones-
density requirement.
Out-Of-Building Station
The Terminal Equipment is directly connected to the System 25, but is not located in
the same building as the common equipment.Special arrangements are made to
protect the system and its users from lightning, power line crosses, etc. Only the
single-line and 7300H series of voice terminal may be so connected. MET Sets can
not be connected as Out-Of-Building stations.
Outside Call
A connection between a system user and a party on the public telephone network or
on a tie trunk.
PDC: (Personal Dial Code)
PFT: (Power Failure Transfer)
Paging Trunk
A telecommunications channel used to access an amplifier for
Parameter
Any set of physical properties whose values determine
performance of a system.loudspeaker paging
the characteristics or
Peripheral Equipment
System Administration Terminal (SAT), SMDR Output device such as a SMDR Printer
or a Call Accounting System, Digital Tape Unit (DTU).
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							GLOSSARY
Personal Dial Code
Each system user is assigned a PDC and is allowed to “sign in” the PDC at any voice
terminal in the system as he or she moves about the premises. The PDC may be a 1-,
2-, 3-, or 4-digit number. There are two types of PDCs:
l PDCs assigned to voice terminals -Associated with each voice terminal in the
system.
l Floating PDCs (FPDCs) -Assigned to visitors and those users who do not
have exclusive use of a voice terminal.An FPDC may be signed in by its
owner at any system voice terminal. Calls to the FPDC will ring at the terminal
where it is signed in.Calls to an FPDC that is not signed in anywhere will
either receive reorder tone or be directed to the attendant (administrable).
Pickup Group
A group of individuals authorized to answer any call directed to an extension number
within the group.
Port
An interface circuit between System 25 and associated auxiliary and peripheral
equipment. Typical references include:
l Terminal port (station port)
l Facility port (trunk port)
l Auxiliary equipment port
Private Branch Exchange (PBX)
A switching system that provides switched communications access amongst its
terminals and facilities (e.g., System 25)
Private Network
A network used exclusively for handling the telecommunications needs of a particular
customer.
Private Network Office Code (RNX)
The first three digits of a 7-digit private network number. These codes are numbered
220 through 999, excluding any codes that have a 0 or 1 as the second digit.
Protocol
A set of conventions or rules governing the format and timing of message exchanges
to control data movement and correction of errors.
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							GLOSSARY
Public Network
The network that can be openly accessed by all customers for local or long-distance
calling.
Queue
An ordered sequence of calls waiting to be processed.
Queuing
The process of holding calls in order of their arrival to await connection to an
attendant, to an answering group, to a station, or to a trunk. Calls are automatically
connected in first-in, first-out sequence.
RIMS: (Remote Initialization and Maintenance Service)
Random Access Memory (RAM)
A storage arrangement whereby information can be retrieved at a speed independent
of the location of the stored information.
Read Only Memory (ROM)
A storage arrangement primarily for information retrieval applications.
Recall Dial Tone
Three short bursts of tone followed by steady dial tone; indicates the system has
completed some action (such as holding a call) and is ready to accept dialing.
Redirection Criteria
The information administered for each voice terminal that determines when an
incoming call is redirected to coverage.
Reorder Tone
A fast-busy tone repeated 120 times a minute; indicates that a call attempt cannot be
completed because, for example, all trunks are busy, a dialing error has occurred,
the terminal is restricted from making the call, or a required account code was not
entered.
Robbed-Bit Signaling
Robbed-bit signaling (RBS) is a transmission format where signaling information is
transmitted in the least significant bit position in each channel every sixth frame.
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							GLOSSARY
SAT: (System Administration Terminal)
SIP: (Station Interconnect Panel)
SLAC: (Switched Loop Attendant Console)
SMDR: (Station Message Detail Recording)
Selector Console: (Direct Extension Selector Console)
Signaling
Signaling is the process of communicating channel state information for end-point to
end-point.
Single-Line Voice Terminal
Voice terminal served by a single-line tip and ring circuit (2500 series and 7101A
voice terminals or industry standard Dual Tone Multifrequency equivalent).
Software
A set of computer programs that accomplish one or more tasks.
Split
A condition whereby a caller is temporarily separated from a connection with the
attendant. This split condition automatically occurs when the attendant, active on a
call, either presses the Start button or uses the Direct Extension Selector Console.
Status LED
A green LED that shows the status of a call appearance or a feature button by the
state of the lamp (lighted, flashing, fluttering, broken flutter, or dark).
Station
A place where terminal equipment is located or sometimes the terminal equipment
itself. Each voice terminal (station) is assigned a station (extension) number. Users
of the terminal are sometimes referred to as station users.Reference to the
extension number is usually in the form PDC (Personal Dial Code) rather than station
number. Though PDCs may be “signed-in”
at other stations, in most discussions
PDCs and station numbers are interchangeable.Analogously, data stations are
assigned DDCs (Data Dial Codes).
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							GLOSSARY
Switch
The software-controlled communications processor complex that interprets dialing
pulses/tones/key board characters and makes the proper interconnections both within
the system and external to the system.The switch itself consists of a digital
computer, software, storage device (memory), and associated circuit packs and
special hardware necessary to perform the actual connections.
Switchhook
The button(s) on a voice terminal located under the handset.
Synchronization
Coordinated timing whereby all switches, channel banks, and multiplexer operate
from the same stable clock reference. The process assures that the transmit and the
distant receive node achieve proper bit alignment.
System Administrator
A person responsible for specifying and administering features and services for the
system.
System Restore
A process that allows stored data to be written from a tape or PC file into the system
memory.
T1
The T1 carrier system is a high speed, time division multiplexed, digital transmission
facility capable of transmitting voice and data at 1.544 Mbps. In System 25, T1 can
replace up to 24 analog trunks,offering improved quality, cost savings, and
enhanced features.
TAE: (Trunk Access Equipment)
Terminal Equipment:
Equipment for changing information (sound, keystrokes) into an electrical signal
compatible with the system’s port circuits (voice and data terminals are two
subdivisions).
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 bus permitting any port to send a signal to any other port.
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