9-1-1 Tandem: The Central Office that provides the tandem switching of 9-1-1 calls. It controls delivery of the voice call with ANI to the PSAP and provides Selective Routing, Speed Calling, Selective Transfer, Fixed Transfer and certain maintenance functions for each PSAP. Also known as Enhanced 9-1-1 Control Office.

Advanced Intelligent Network (AIN): A telephone network architecture that separates service logic from switching equipment, allowing new services to be added without having to redesign switches to support new services.

ALI Retrieval: A request for ALI record from the PSAP to the ALI database.

Angle of Arrival (AOA): A terrestrial Location Determination Technology (LDT) that computes a transmitter's location based upon the angle at which the transmitter's radio signal strikes multiple receivers.

Automatic Location Identification (ALI): The automatic display at the PSAP of the caller's telephone number, the address/location of the telephone and supplementary emergency services information.

Automatic Location Identification (ALI) Database: The set of ALI records residing on a computer system.

Automatic Number Identification (ANI): Telephone number associated with the access line from which a call originates.

Calling Party's Number (CPN): The callback number associated with a wireless telephone. (Similar to ANI for wireline telephones.)

Cell: The wireless telecommunications (Cellular or PCS) antenna serving a specific geographic area.

Cell Face: (See Cell Sector)

Cell Sector: One face of a cell antenna (typically 3-sided) that operates independently of the other sectors.

Cell Site: The location of a cell and related equipment.

Central Office (CO): The Local Exchange Carrier facility where access lines are connected to switching equipment for connection to the Public Switched Telephone Network.

Class of Service: A designation of the type of telephone service, e.g. residential, business, centrex, coin, PBX, wireless.

Computer Aided Dispatch (CAD): A computer-based system that aids PSAP attendants by automating selected dispatching and record keeping activities.

Database: An organized collection of information, typically stored in computer systems, comprised of fields, records (data) and indexes. In 9-1-1, such databases include MSAG, telephone number/ESN and telephone customer records.

Dedicated Trunk: A telephone circuit used for a single purpose, such as transmission of 9-1-1 calls.

Emergency Call: A telephone request for public safety agency emergency services that requires immediate action to save a life, to report a fire or to stop a crime. May include other situations as determined locally.

End User: The 9-1-1 caller.

Enhanced 9-1-1 (E9-1-1): An emergency telephone system which includes network switching, database and CPE elements capable of providing selective routing, selective transfer, fixed transfer, ANI and ALI.

Enhanced 9-1-1 (E9-1-1) Control Office: The Central Office that provides the tandem switching of 9-1-1 calls. It controls delivery of the voice call with ANI to the PSAP and provides selective routing, speed calling, selective transfer, fixed transfer and certain maintenance functions for each PSAP. Also known as 9-1-1 Selective Routing Tandem or Selective Router.

Exchange: A defined area, served by one or more telephone central offices, within which a Local Exchange Carrier furnishes service.

Global Positioning System (GPS): A satellite-based Location Determination Technology (LDT).

Local Exchange Carrier (LEC): A Telecommunications Carrier (TC) under the state/local Public Utilities Act that provides local exchange telecommunications services. Also known as Incumbent Local Exchange Carriers (ILECs), Alternate Local Exchange Carriers (ALECs), Competitive Local Exchange Carriers (CLECs), Competitive Access Providers (CAPs), Certified Local Exchange Carriers (CLECs) and Local Service Providers (LSPs).

Local Number Portability (LNP): A process by which a telephone number may be reassigned from one Local Exchange Carrier to another.

Location Determination Technology (LDT): A system that computes the X and Y coordinates of a wireless 9-1-1 caller.

Mobile Directory Number (MDN): (see Calling Party's Number (CPN))

Mobile Switching Center (MSC): The wireless equivalent of a Central Office, which provides switching functions from wireless calls.

Multi-Frequency (MF): A type of signaling used on analog interoffice and 9-1-1 trunks.

National Emergency Number Association (NENA): The National Emergency Number Association is a not-for-profit organization established in 1982 to further the goal of "One Nation-One Number." NENA is a networking source and promotes research, planning and training. NENA strives to educate, set standards and provide certification programs, legislative representation and technical assistance for implementing and managing 9-1-1 systems.

Numbering Plan Digit (NPD): A component of the traditional 9-1-1 signaling protocol between the 9-1-1 Control Office and the PSAP CPE. Identifies 1 of 4 possible area codes.

Primary Public Safety Answering Point (PSAP): A PSAP to which 9-1-1 calls are routed directly from the 9-1-1 Control Office. (See PSAP)

Pseudo Automatic Location Identification (PALI): An ALI record associated with a PANI, configured to provide the location of the wireless cell or sector and information about its coverage or serving area (footprint).

Pseudo Automatic Number Identification (PANI): A telephone number used to support routing of wireless 9-1-1 calls. It may identify a wireless cell, cell sector or PSAP to which the call should be routed. Also known as routing number.

Public Safety Agency: An entity that provides firefighting, law enforcement, emergency medical or other emergency service.

Public Safety Answering Point (PSAP): A facility equipped and staffed to receive 9-1-1 calls. A Primary PSAP receives the calls directly. If the call is relayed or transferred, the next receiving PSAP is designated a Secondary PSAP.

Signaling System 7 (SS7)/Common Channel Signaling 7 (CCS7): An inter-office signaling network separate from the voice path network, utilizing high-speed data transmission to accomplish call processing. (The Public Switched Telephone Network is in the process of upgrading from MF Signaling to SS7.)

Tandem Central Office (Tandem CO): (See E9-1-1 Control Office)

Telecommunicator: As used in 9-1-1, a person who is trained and employed in public safety telecommunications. The term applies to call-takers, dispatchers, radio operators, data terminal operators or any combination of such functions in PSAP.

Time Difference of Arrival (TDOA): A terrestrial Location Determination Technology (LDT) that computes a transmitter's location based upon the times a signal is received at multiple receivers.

Trunk: Typically, a communication path between central office switches, or between the 9-1-1 Control Office and the PSAP.

Wireless Phase I: Required by FCC Report and Order 96-264 pursuant to Notice of Proposed Rulemaking (NPRM) 94-102. The delivery of a wireless 9-1-1 call with callback number and identification of the cell-sector from which the call originated. Call routing is determined by cell-sector.

Wireless Phase II: Required by FCC Report and Order 96-264 pursuant to Notice of Proposed Rulemaking (NPRM) 94-102. The delivery of a wireless 9-1-1 call with Phase I requirements plus location of the caller within 125 meters 67 percent of the time and selective routing based upon those coordinates.

Wireless Telecommunications: The family of telecommunications services under the heading of Commercial Mobile Radio Service. Includes Cellular, Personal Communications Services (PCS), Mobile Satellite-Services (MSS) and Enhanced Specialized Mobile Radio (ESMR).

X/Y: X = Longitude, Y = Latitude. Longitude is an East-West measurement and latitude is a North-South measurement. X/Y data are in the Geographic Coordinate Datum NAD83. Units are in decimal degree format.

Glossary Reference: provided by NENA.