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Electrodata, Inc. – Audio, DS0, T1, T3, and STS1 SONET handheld and remote test equipment designed to make telecommunications problem-solving easier.

This list of telecommunications acronyms relates primarily to T1, DS3, and STS-1 SONET telecommunications, but has been steadily growing to include a broader range of telecom subjects such as GR-303, SS7, ATM, etc., as well as signal abbreviations used with some protocols. These acronyms are presented as they appear in industry standards and various professional industry publications. Click on the initial letter below. To return to the top of the page, click on your browser’s “BACK” button.





aoc	ADSL overhead control channel
AA Administrative Authority
AAL ATM Adaptive Layer
AAR Automatic Alternate Routing
ABR Available Bandwidth Rate
ABR Available Bit Rate
ACD Automatic Call Distribution
ACF Access Coordination Function
ACK Acknowledgment
ACM Adress Complete Message
ACO Automatic Cut Off
ACSE Association Control Service Element
ACU Alarm Control Unit
ADC Analog to Digital Converter
ADM Add/Drop Multiplexer
ADM 3X DS3 Add-Drop Multiplex
ADPCM Adaptive Differential Pulse Code Modulation
ADSI Analog Display Services Interface
ADSL Asymmetric Digital Subscriber Line
ADSS All Dielectric Self-Supporting
ADTS Automated Digital Terminal Systems
AERM Alignment Error Rate Monitor
AFI Authority and Format Identifier
AFSK Audio Frequency Shift Keying
AFPS Automatic Facility Protection Switching
Ai Action indicator
AIN Advanced Intelligent Network
AIS Alarm Indication Signal
AIS-L Alarm Indication Signal - Line
AIS-P Alarm Indication Signal - Path
AIS-V Alarm Indication Signal - Virtual (Tributary)
AIU Analog Interface Unit
ALIT Automatic Line Insulation Test
ALPS Automatic Loop Protection Switching
AMA Automatic Message Accounting
AMI Alternate Mark Inversion
AMPS Advanced Mobile Phone Service
ANC Access network Controller
ANI Automatic Number Identification
ANM Answer Message (Pick Up)
ANSI American National Standards Institute
AON All Optical Network
AP Access Point
AP Action Point
APDU Application Protocol Data Unit
APR Alarm Processing Remote
APS Automatic Protection Switching
ARD Automatic Ring Down
ARP Address Resolution Protocol
AS56 Accunet Switched 56
ASB Application Specific Bits
ASC Abnormal Station Code
ASCII American Standard Code for Information Interchange
ASN.1 Abstract Syntax Notation One
ASP Application Service Provider
ASP Assignment Source Point
AT Access Tandems
ATM Asynchronous Transfer Mode
ATM-LI ATM Link Identifier
ATM-PCI ATM Protocol Control Information
ATM-SDU ATM Service Data Unit
ATMM ATM Layer Management
ATU-C ADSL Transceiver Unit - Central office end
ATU-R ADSL Transceiver Unit - Remote terminal end


B3ZS	Bipolar 3 Zero Substitution
B6ZS Bipolar 6 Zero Substitution
B8ZS Bipolar 8 Zero Substitution
B8ZS Bipolar 8 Zero Suppression
B-CPE Broadband Customer Premises Equipment
B-ICI Broadband Inter-Carrier Interface
BAF Bellcore AMA Format
Bc Committed Burst Size
BCD Binary Coded Decimal
BCM Bit Compression Multiplexer
BDFB Battery Distribution Fuse Board
BDCBB Battery Distribution Circuit Breaker Board
BE Block Error
BECN Backward Explicit Congestion Notification
BER Basic Encoding Rules
BER Bit Error Ratio
BERT Bit Error Rate Tester
BFCV Binary Facility Coding Value
BGP Border Gateway Protocol
BIB Backward Indicator Bit
BIBR Backward Indicator Bit Received
BIBT Backward Indicator Bit to be Transmitted
BIBX Backward Indicator Bit eXpected
BIP Bit Interleaved Parity
BISDN Broadband Integrated Services Digital Network
BISUP Broadband ISUP (ISDN User Part)
BLER Block Error Rate
BOC Bell Operating Company
BOM Beginning of Message
BORSCHT Battery feed, Overvoltage protection, Ringing, Signaling, Coding, Hybrid, and Testing
BPOP Building Point of Presence
bps Bits Per Second
BPV Bipolar Violation
BRA Basic Rate Access
BRI Basic Rate Interface (ISDN)
BRITE Basic Rate Interface Transmission Extension
BSC Base Station Controller
BSC Bisynchronous Communications (protocol)
BSN Backward Sequence Number
BSNR Backward Sequence Number Received
BSNT Backward Sequence Number to be Transmitted
BSP Bell System Practice
BSRF Basic System Reference Frequency
BSS Base Station Subsystem
BSS Basic Service Set
BSS Broadband Switching System
BTS Base Station Transceiver


C/R	Command/Response
C/R Control/Response Indication Bit
CAC Connection Admission Control
CAL Customer Access Line
CAP Carrierless Amplitude Phase (modulated)
CAP Competitive Access Provider
CAS Channel Associated Signaling
CATV Cable television
CBCU Centralized Broadband Control Unit
CBDS Connectionless Broadband Data Services
CBR Constant Bit Rate
CBQ Class-Based Queuing
Cc Committed Burst Size
CCC Clear Channel Capability
CCE Consistency Check End
CCS Hundred Call Seconds
CCIS Common Channel Inter-office Signaling
CCITT Comite Consultatif Internationale Telegraphique et Telephonique
CCITT International Telegraph and Telephone Consultative Committee
CCR Consistency Check request
CCR Customer Controlled Reconfiguration
CCS Common Channel Signaling
CCS Hundred Call Seconds
CCSA Common Control Switching Arrangement
CCU Common Control Unit
CDMA Code Division Multiple Access
CDO Community Dial Office
CDPD Cellular Digital Packet Data
CEI Connection Endpoint Identifier
CEPT Committee of European Postal & Telephone (authorities)
CES Circuit Emulation Service
CES Connection Endpoint Suffix
CEV Controlled Environment Vault
CF Coin First
CFA Carrier Failure Alarm
CFA Connecting Facility Assignment
CGA Carrier Group Alarm
CGW Customer Gateway
CH Cell Header
CHTML Compact Hyper Text Markup Language
CI Customer Installation
CIC Circuit Identification Code
CID Craft Interface Device
CIR Committed Information Rate
CIU Communications Interface Unit
CLEC Competitive Local Exchange Carrier
CLLM Consolidated Link Layer Management
CLNP Connectionless-mode Network Protocol
CLNS Connectionless Network Services
CLP Cell Loss Priority (CLP Bit)
CLS Connectionless Service
CMIP Common Management Information Protocol
CMIS Common Management Information Service
CMISE Common Management Information Service Element
CNM Customer Network Management
CO Central Office
COC Central Office Connection
COFA Change of Frame Alignment
COM Continuation of Message
COPS Common Open Policy Service
CORBA Common Object Request Broker Architecture
COT Central Office Terminal
CP Cell Payload
CP Customer Premises
CPCS Common Part Convergence Sublayer
CPE Customer Premises Equipment
CPI Computer-PBX Interface
CPNI Customer Proprietary Network Information
CPP Calling Party Pays
CPS Customer Premises System
CPU Central Processor Unit
CR Call Reference
CRC Cyclic Redundancy Checkword
CRM Circuit Reservation Message
CRS Cell relay Service
CRV Call Reference Value
CS Convergence Sublayer
CSA Canadian Standards Association
CSA Carrier Service Area
CSAP Core Service Access Point
CSC Common Signaling Channel
CSDU Core Service Data Unit
CSH Convergence Sublayer Header
CSMA/CD Carrier Sense Multiple Access/Collision Detect
CU Channel Unit
CS Convergence Sublayer
CSA Carrier Serving Areas
CSR Consistency Check Request
CST Convergence Sublayer Trailer
CSU Channel Service Unit
CS-PDU Convergence Sub-layer PDU
CT Channel Termination
CT Computer Telephony
CTU Channel Test Unit
CU Channel Unit
CUG Closed Users Group
CV Coding Violation
CVSD Continuously Variable Slope Delta Modulation
CPE Customer Premise Equipment
CPI Computer-PBX Interface
CQM Circuit Query Message
CQR Circuit Query Response
CTS Clear to Send
CV Coding Violation
CUG Closed Users Group
CVSD Continuously Variable Slope, Delta Modulation
CWC Center Weight Control



DA	Distribution Area
DACS Digital Access and Cross Connect
DAVIC Digital Audio Video Council
DBS Direct Broadcast Satellite
dB deciBell
dBm dB relative to one milliwatt
DBN Dial-Back Number
dBrn dB relative to noise
dBrnc dB relative to noise (C-Notch or C-Message)
DCB Digital Channel Bank
DCC Data Communications Channel
DCC Data Country Code
DCCX Direct Circuit Control Exchange
DCE Data Circuit-terminating Equipment
DCE Data Communications Equipment
DCF Distributed Coordination Function
DCN Data Communications Network
DCS Digital Cross-connect
DCSs Digital Cross-Connect System
DDD Direct Distance Dialing
DDS Dataphone Digital Service (registered trademark of AT&T C0.)
DDS Digital Data Service
DDSD Delay Dial Start Dial
DE Discard Eligibility
DF Distributing Frame
DFL Distributed Feedback Laser
DFRI Datacom Reference Frame Input
DHCP Dynamic Host Configuration Protocol
DID Directed Inward Dialing
DL Data Link
DLC Digital Loop Carrier
DLCI Data Link Connection Identifier
DLL Dial Long Line
DLU Digtal Line Unit
DM Disconnected Mode
DMI Digital Multiplex Interface
DMPB Digital Multipoint Bridging
DMS Digital Multiplex System
DMT Discrete Multitone
DNIC Data Network Identification Code
DNIC Data Network Interface (2B+D ISDN)
DNIS Dialed Number Identification Service
DNS Domain Name System
DOCSIS Data Over Cable Service Interface Specification
DoV Data Over Voice
DP Dial Pulse
DPA Distributed Power Architecture
DPBX Digital Private Brance Exchange
DPC Destination Point Code
DPCM Differential Pulse Code Modulation
DPDU Data (link) Protocol Data Unit
DPL Digital Power Line
DPO Dial Pulse Originate
DPT Dial Pulse Terminate
DPT Dynamic Packet Transport
DS0 Digital Signal Zero - 64 Kb/s data/voice chan
DS1 Digital Signal One (DS0 x 24 mux = 24 DS0)
DS2 Digital Signal 2 (DS1 x 4 mux = 96 DS0)
DS3 Digital Signal 3(DS2 x 7 mux = 672 DS0)
DSI Digital Speech Interpolation
DSL Digital Subscriber Line
DSLAM Digital Subscriber Line Access Multiplexer
DSODP Digital Service Office Dataport
DSP Digital Signal Processor
DSSS Direct Sequence Spread Spectrum
DSU Digital Service Unit
DSX Digital Signal Cross-connect
DSSS Direct Sequence Spread Spectrum
DTAU Digital Test Access Unit
DTE Data Terminal Equipment
DTF Dial Tone First
DTF Digital Transmission Facility
DTI Digital Trunk Interface
DTMF Dual Tone Multiple Frequency
DTR Data Terminal Ready
DTS Digital Terminal Systems
DTS Digital Transmission Systems
DTU Data Terminal Unit
DTX Discontinuous Transmission
DUP Data User Part
DVI Digital Video Interleaved
DWDM Dense Wavelength Division Multiplexing
DX Duplex
DXC Digital Cross Connect
DXI Data Exchange Interface
D/I Drop and Insert
D3 Third generation channel bank (24 chans on T1)
D4 Fourth generation channel bank (48 voice chans on 2 T1's or 1 T-1C)


EA	Extended Address
EAI Enterprise Application Integration
EBCDIC Extended Binary Coded Decimal Information Code
EC Echo Canceling
EC-n Electrical Carrier (e.g., EC-1)
ECSA Exchange Carriers Standards Association
EDFA Erbium-Doped Fiber Amplifier
EDI Electronic Data Interchange
EDSX Electronic Digital Signal Cross-Connect
EFCI Explicit Forward Congestion Indication
EFD Event Forwarding Discriminator
EFS Error Free Second
EGP Exterior Gateway Protocol
EIM Errored Interval Monitored
ELEC Ethernet Local Exchange Carrier
ELFEXT Equal Level Far End Crosstalk
EM Element Manager
EML Element Management Layer
EMI Electromagnetic Interference
EMS Element Management System
EOC Embedded Operations Channel
EOM End of Message
EPSCS Enhanced Private Switch Controlled System
ERL Echo Return Loss
ERM Explicit Rate Marketing
ES Errored Second
ESF Extended Super Frame
ESG Enhanced Service Gateway
ESFDL Extended Super Frame Data-Link
ESI End System Identifier
ESS Electronic Switching System
ET Exchange Termination
ETN Electronic Tandem Network
ETSI European Telecommunications Standards Institute
EXZ Excess Zeros


FAS	Frame Alignment Signal
FAW Frame Alignment Word
FB Framing Bit
FBWA Fixed Broadband Wireless Access
FCC Federal Communications Commission
FCS Frame Check Sequence
FDDI Fiber Distributed Data Interface
FDI Feeder Distribution Interface
FDL Facilities Data Link
FDLC Fujitsu Digital Loop Carrier
FDM Frequency Division Multiplexing
FE Frame synchronization bit error Event
FEAC Far End Alarm and Control
FEBE Far End Block Error
FEBE-f Far End Block Error Count - fast data
FEBE-i Far End Block Error Count - interleaved data
FEC Forward Error Correction
FECC-f Forward Error Correction Count - fast data
FECC-i Forward Error Correction Count - interleaved data
FECN Forward Explicit Congestion Notification
FELB Far End Loop Back
FERF Far End Receive Failure
FEXT Far-End Cross Talk
FHSS Frequency Hopping Spread Spectrum
FI Facility Identification
FIB Forward Indicator Bit
FIBR Forward Indicator Bit Received
FIBT Forward Indicator Bit to be Transmitted
FIBX Forward Indicator Bit eXpected
FIC Frame Identification Code
FIFO First In First Out
FISU Fill-In Signal Unit
FITL Fiber In The Loop
FLL Fixed Loss Loop
FOTS Fiber Optical Transmission System
FPS Framing Pattern Sequence
FR-SSCS Frame Relay Service Specific Convergence Sub-layer
FRAD Frame Relay Access Device
FRAD Frame Relay Assembler/Disassembler
FRF-LMI Frame Relay Forum - Local Management Interface
FRMR Frame Reject
FR PVC Frame Relay Permanent Virtual Connection
FRS Frame Relay Service
FRSS Frame Relay Switching System
FSK Frequency Shift Keying
FSN Forward Sequence Number
FTAM File Transfer, Access and Management
FTP File Transfer Protocol
FTSC Federal Telecommunications Standards Committee
FTTC Fiber to the Curb
FTTH Fiber to the House
FTTL Fiber to the Loop
FTTN Fiber to the Neighborhood
FT1 Fractional T1
FUNI Frame (relay) User Network Interface
FXO Foreign Exchange Office
FX Foreign Exchange
FXO Foreign Exchange Office
FXS Foreign Exchange Subscriber


GFC	Generic Flow Control
GFI General Format Identifier
GGP Gateway to Gateway Protocol
GGSN Gateway GPRS Support Node
GOS Grade of Service
GOSIP Government Open System Interconnection Profiles
GPRS General Packet Radio Service
GPRS General Packet Radio System
GPS Global Positioning System
GS Ground Start
GSM Global System for Mobile (telecommunications)
GTXC Global Telephone Exchange Carrier


HCDS	High Capacity Digital Services
HCV High Capacity Voice
HDB3 High-Density Bipolar Three-Bit substitution
HDLC High (level) Data Link Control
HDML Handheld Device Markup Language
HDSL High (Data Rate) Subscriber Line
HDSL2 High (Data Rate) Subscriber Line (w/6dB noise margin)
HDT Host Digital Terminal
HEC Header Error Control
HFC Hybrid Fiber Coax
HLR Home Location Register
HPC High Probability of Completion
HSCWD High Speed Circuit Switched Data
HTML Hypertext Markup Language
HTTP Hypertext Transfer Protocol
HTU HDSL Transmission Unit
HTU-C HDSL Transmission Unit - Central Office
HTU-R HDSL Transmission Unit - Remote


IAA	Initial Address Acknowledgement
IAB Internet Advisory Board
IAC Initial Alignment Control
IAD Integrated Access Device
IAM Initial Address Message
IAR Initial Address Reject
IAT Integrated Access Terminal
IC-POT Interexchange Carrier-Point of Termination
ICCF Interexchange Carrier Compatibility Forum
ICD International Code Designator
ICI Inter-Carrier Interface
ICIP Inter-Carrier Interface Protocol
ICL Inserted Connection Loss
ICMP Internet Control Message Protocol
ICOT Inner City and Outstate Trunk
IDCP Internet Device Control Protocol
IDF Intermediate Distribution Frame
IDLC Integrated Digital Loop Carrier
IDS Intrusion Detection System
IDT Information Distribution Company
IDT Integrated Digital Terminal
IDU Interface Data Unit
IEEE Institute of Electrical and Electronics Engineers
IG Interface Group
IGP Interior Gateway Protocol
IIME Intra-network, Inter-SSS Mapping Entity
IIS Internet Information Server
ISID Idle Signal Identification
ISSP Interim Interswitch Signaling Protocol
ILEC Incumbent Local Exchange Carrier
ILEC Independent Local Exchange Carrier
ILMI Interim Local Management Interface
IMP Interface Message Processors
IMS Interactive Multimedia Server
IMSI International Mobile Subscriber Identity
IN Intelligent Network
INA Information Network Architecture
INE Intelligent Network Element
IO Inter-Office
IOC Inter-Office Channel
IP Intelligent Peripheral
IP Internet Protocol
IPSec Internet Protocol Security
IPM Interpersonal Messaging System
IPS Instructions Per Second
ISDN Integrated Services Digital Network
ISDNUP Integrated Services Digital Network User Part
ISM Instrumentation, Scientific, and Medical
ISO International Standards Organization
ISP Internet Service Provider
ISSI Inter-Switching System Interface
ISSIP Inter-Switching System Interface Protocol
ITFS Instructional Television Fixed Services
ITU International Telecommunication Union
IWF Inter-Working Function
IWU Inter-Working Unit
IXC Interexchange Carrier


JIS	Jurisdictional Interstate Service




LAN	Local Area Network
LAN PHY LAN Physical Layer
LANE Local Area Network Emulation
LAP-D Link Access Protocol-D channel
LAPB Link Access Protocol Balanced
LAPD Link Access Procedure D channel
LATA Local Access and Transport Area
LAW Local Area Wireless
LC Load Coil
LC Loop Closure
LCA Line Circut Address
LCF Loop Current Feed
LCFO Loop Current Feed Open
LCGN Logical Channel Group Number
LCN Logical Channel Number
LCP Link Control Protocol
LDAP Lightweight Directory Access Protocol
LDC LATA Distribution Channel
LDF Local Distribution Frame
LDM Limited Distance Modem
LDN Listed Directory Number
LDP Label Distribution Protocol
LDS Local Digital Switch
LEC Local Exchange Carrier
LEN Line Equipment Number
LES LAN Emulation Services
LET Line Equipment Transfer
LGE Loop- or Ground-Start Exchange
LGS Loop- or Ground-Start Subscriber
LIDB Line Information Database
LLB Line Loop Back
LLC Logical Link Control
LLSC signaling Link management; Link Set Control
LMC Loop Maintenance Center
LMDS Local Multipoint Distribution Service
LMI Local Management Interface
LMOS Loop Maintenance Operations System
LMU Line Monitor Unit
LNP Local Number Portability
LO Loop Open
LOF Loss Of Frame
LOH Line Overhead
LOP Loss Of Pointer
LOP-L Loss Of Pointer - Line
LOP-P Loss Of Pointer - Path
LOP-V Loss Of Pointer - Virtual
LOS Line of Sight
LOS Loss Of Signal
LOSW Loss Of Synchronous Word
LPC Linear Predictive Coding
LPDP Local Policy Decision Point
LPU Line Protection Unit
LRB Loop Reverse Battery
LRN Local Routing Number
LS Loop Start
LSAC signaling Link management; Signaling Link Activity Control
LSAP Link Service Access Point
LSC Link State Control
LSLA signaling Link management; Signaling Link Activation
LSLD signaling Link management; Signaling Link Deactivation
LSLR signaling Link management; Signaling Link Restoration
LSMS Local Service Management System
LSOA Local Service Order Administration
LSR Label Switching Router
LSSGR LATA Switching Systems Generic Requirements
LSSU Link Status Signal Unit
LSU Line Switch Unit
LT Line Termination
LTE Line Terminal Equipment
LU Line Unit
LULT Line Unit/Line Termination
LUNT Line Unit Network Termination
LXT Local Exchange Terminal


MAC	Media Access Control
MAN Metropolitan Area Network
MAPDU Management Application Protocol Data Unit
MAT Metropolitan Area Trunk
MB Maintenance Busy
MCC Mobile Country Code
MCU Multiplexer Control Unit
MDCP Media Device Control Protocol
MDF Main Distribution Frame
MDS Multipoint Distribution Service
MDTP Media Device Transport Protocol
MF Multiple Frequency
MFAS Multi-Frame Alignment Signal
MGCP Media Gateway Control Protocol
MRF Multilink Frame Relay
MGCP Media Gateway Control Protocol
MIB Management Information Base
MIME Multipurpose Internet Mail Extension
MIX Multimedia Internet Exchange
MJU Multi-Junction Unit
MLHG Multi-Line Hunt Group
MLM Multi-Longitudinal Mode
MLT Mechanized Loop Testing
MLT Metalic Loop Test
MMDX Multimedia Data Services
MMDS Multichannel Multipoint Distribution Service
MMDS Multimedia Data Services
MO Managed Object
MOC Managed Object Classes
MOOS Manual Out-OF-Service
MPLS Multi-Protocol Label Switching
MPLS Multi-Protocol Layer Switching
MPoA Multiple Protocol over ATM
MSA Metropolitan Statistical Area
MSDM Multipoint Substrate Data Mux
MSO Multiple Service Operator
MTAU Metalic Test Access Unit
MTP Message Transfer Part
MRVT MTP Routing Verification Test
MTS Message Telephone System
MTSO Mobile Telephone Switching Office
MUB MultiUse Bearer service
MULDEM MULtiplexer/DEMultiplexer
MUX MULtiplexer/DEMultiplexer
MVNO Mobile Virtual Network Operator


N(r)	Receive Sequence Number
N(s) Send Sequence Number
NACK Negative ACKnowledgement
NADH North American Digital Hierarchy
NAK Negative Acknowledgement
NANP North American Numbering Plan
NAS Network Attached Storage
NAT Network Attached Storage
NAT Network Address Translation
NC Network Channel
NCC Network Communications Controller
NCI Network Channel Interface
NCP Network Control Point
NCP Network Control Protocol
NCTE Network Channel Terminating Equipment
NDF New Data Flag
NE Network Element
NEXT Near End Cross Talk
NFAS Non-associated Facility Signaling
NGDLC Next Generation Digital Loop Carrier
NGN Next Generation Network
NGW Network Gateway
NI Network Interface
NI Network Interface
NI-1 National ISDN-1
NI-2 National ISDN-2
NIC Network Interface Card
NIU Network Interface Unit
NLPID Network Level Protocol ID
NLOS Near Line of Sight
NMA Network Management and Administration
NMA Network Monitoring and Analysis
NMC Network Management Center
NML Network Management Layer
NMP Network Management Protocol
NMS Network Management System
NNI Network Node Interface
NNI Network-to-Network Interface
NNTP Network News Transport Protocol
NOC Network Operations Center
NOS Network Operating System
NOTE Network Office Terminating Equipment
NPA Numbering Plan Area
NPAC Number Portability Administration Center
NPDU Network Protocol Data Unit
NPRN Network Performance Report Message
NPI Numbering Plan Identification
NRIC National Reliability and Interoperatability Council
NRZ Non-Return to Zero
NSA Non-Service Affecting
NSC Network Service Center
NSF Network Specific Facilities
NSI Network Service Interface
NSP National Signaling Point
NTE Network Terminating Equipment
NTT Numbered Test Trunk
NYIIX New York International Internet Exchange


OADM	Optical Add-Drop Multiplexer
OAM Operations, Administration, and Maintenance
OAM&P Operations, Administration, Maintenance & Provisioning
OAMP Operations, Administration, Maintenance Provisioning
OC-n Optical Carrier (e.g., OC-3)
OC-x Optical Carrier (e.g., OC-3)
OCPD Over Current Protection Device
OCU Office Channel Unit
OCUDP Office Channel Unit Data Port
OE Originating Equipment
OEO Optical-Electrical-Optical
OFA Optical Fiber Amplifier
OFDM Orthogonal Frequency Division Multiplexing
OIM Operations Interface Module
OLNS Originating Line Number Screening
OLP On-Line Provisioning
OM Operational Measurement
ONU Optical Network Unit
OOD Object Oriented Design
OOF Out Of Frame
OOS Out Of Service
OOS Out Of Synchronization
OPN Outage Performance Monitoring
OPS/INE Operations System/Intelligent Network Element
OPX Off Premise Extension
OR Office Regenerator
ORB Office Repeater Bay
OS Operations System
OSI Open System Interconnection
OSI Open System Interface
OSPF Open Shortest Path First
OSS Operation Support System
OSS Operator Services System
OTC Operating Company
OTDR Optical Time Domain Reflectometer
OUI Organizationally Unique Identifier


P/F	Poll/Final Bit
PA Pointer Adjustment
PABX Private Automatic Branch Exchange
PAD Packet Assembler / Disassembler
PAM Pass Along Message
PAM Pulse Amplitude Modulation
PAW Personal Area Wireless
PBD Power Board
PBX Private Branch Exchange
PCF Point Coordination Function
PCI Protocol Control Information
PCM Pulse Code Modulation
PCMCIA Personal Computer Memory Card International Association
PCS Personal Communications Services
PCTF Per-Call Test Failure
PCU Packet Control Unit
PD Protocol Discriminator
PDH Plesiochronous Digital Hierarchy
PDI-P Payload Defect Indicator - Path
PDI V Payload Defect Indicator - Virtual
PDN Public Data Network
PDP Policy Decision Point
PDU Protocol Data Unit
PEP Policy Enforcement Point
PFDL Policy Framework Definition Language
PFM Packet Forwarding module
PGTC Pair Gain Test Controller
PGS Pair Gain System
PHS Packet Handling System
PHY Physical Layer (abbrev.)
PHY-PCI Physical Layer Protocol Control Information
PHY-SAP Physical Layer-Service Access Point
PHY-SDU Physical Layer-Service Data Unit
PHYM Physical Layer Management
PIB Policy Information Base
PID Path Identification
PIP Pre-Impulsing Pulse
PJC Pointer Justification Count
PKI Public Key Infrastructure
PL Private Line
PLA Programmable Logic Array
PLAR Private Line Automatic Ringdown
PLB Payload Loop Back
PLC Power Line Carrier
PLCP Physical Layer Convergence Protocol
PLS Private Line service
PM Performance Monitoring
PMD Physical Media Dependent
PNNI Private Network Node Interface
POC Positive Outage Control
POH Path Overhead
PON Passive Optical Network
POP Point Of Presence
POP Post Office Protocol
PoS Packet Over SONET
POS Point of Sale
POT Point Of Termination
POTS Plain Old Telephone Service
POTS Plain Old Telephone System
PPP Point to Point Protocol
PPSN Public Packet Switched Network
PRA Primary Rate Access
PRD Pseudo-Random Downstream
PRI Primary Rate Interface (ISDN)
PRBS Pseudo-Random Binary Sequence
PRBS Pseudo-Random Bit Sequence
PRM Performance Report Message
PRS Primary Reference Source
PRU Pseudo-Random Upstream
PSELFEXT Power Sum Equal Far End Cross Talk
PSDM Premium Substrate Data Mux
PSDS Public Switched Digital Service
PSK Pulse Shift Keying
PSNEXT Power Sum Near End Cross Talk
PSTN Public Switched Telephone Network
PSX Power System Exchange
PT Payload Type
PTE Path Terminal Equipment
PTI Payload Type Indicator
PTT Postal, Telephone and Telegraph Authority
PVC Permanent Virtual Circuit


QAM	Quadrature Amplitude Modulation
QoS Quality of Service
QPA Quality Performance Analysis
QRS Quasi Random Signal
QRSS Quasi Random Signal Sequence


R	Ring
RAD Remote Antenna Driver
RAI Remote Alarm Indication
RALB Resource All Busy
RARP Reverse Address Resolution Ptotocol
RAS Remote Access Server
RAS Remote Access Service
RASP Remote Antenna Signal Processing
RBOC Regional Bell Operating Company
RBS Robbed Bit Signaling
RC Retransmission Counter
RCC Release Cause Code
RCV Receive
RD Routing Domain
RDF Remote Distribution Frame
RDI Remote Defect Indicator
RDI-L Remote Defect Indicator - Loop
RDI-P Remote Defect Indicator - Path
RDI-V Remote Defect Indicator - Virtual
RDT Remote Digital Terminal
RE Relaying Entity
REL Release Message
REN Ringer Equivalent Number
RFCs Request For Comments
RFI Radio Frequency Interference
RIP Routing Information Protocol
RLC Release Complete
RLCI Receive Line Clock Input
RLDI Receive Line Data Input
RM Resource Management
RNC Radio Network Controller
RNR Receive Not Ready
ROH Receiver Off Hook
ROS Remote Operations Service
ROSE Remote Operations Service Element
RPR Resilient Packet Ring
RR Receive Ready
RSS Remote Switching Sites
RSS Remote Switching System
RSU Remote Switching Unit
RT Remote Terminal
RTA Rural Trading Area
RTB Retransmission Buffer
RTPC signaling Route management; Transfer Prohibited Control
RTR Retransmission indicator
RTS Request To Send
RTU Remote test Unit
RX Receive
RZ Return to Zero


SAA	Service Adaptive Access
SABME Set Asynchronous Balance Mode Extender
SAN Storage Area Network
SAM Service Access Multiplexer
SAMI SAM Interface
SAN Storage Area Network
SAP Service Access Point
SAPI Service Access Point Indetifier
SAR Segmentation And Reassembly
SAR-PDU Segmentation and Reassembly PDU
SBX Small Business Exchange
SC-FDE Single Carrier Frequency Domain Equalization
SCC Switching Control Center
SCCP Signaling Connection Control Part
SCCS Switching Control Center System
SCE Service Creation Environment
SCP Service Control Point
SDCU Synchronous Data Channel Unit
SDH Synchronous Digital Hierarchy (SONET)
SDLC Synchronous Data Link Control
SDP Session Description Protocol
SDM Substrate Data Mux
SDN Software Defined Network
SDP Service Definition and Provisioning
SDP Session Description Protocol
SDSL Symmetric Digital Subscriber Line
SEAL Simple and Efficient Adaptation Layer
SEL Selector Field
SEFL Single Ended Fault Locating
SEP Signaling End Point
SES Severe Errored Seconds
SF Single Frequency
SF Status Field
SF Superframe
SGCP Simple Gateway Control Protocol
SGML Standard Generic Markup Language
SGSN Serving GPRS Support Node
SH SAR Sublayer Header
SHR Self-Healing Ring
SINAD Signal-to-Noise Plus Distortion (ratio)
SI Service Information octet
SIB Status Indication B (busy)
SIE Status Indication E (emergency alignment)
SIF Signaling Information Field
SIN Status Indication N (normal alignment)
SIO Status Indication O (out of alignment)
SIP Session Initiation Protocol
SIT Special Information Tone
SL Service Layer
SLA Service Level Agreement
SLIC Subscriber Line Interface Card
SLIP Serial Line Interface Protocol
SLIP Serial LIne Internet Protocol
SLS Single Link Set
SMASE Systems Management Application Service Element
SMC Switch Maintenance Center
SMDF Subscriber Maintenance Distributing Frame
SMDS Switched Multi-megabit Data Service
SML Service Management Layer
SMS Service Management System
SMS Short Message Service
SMTP Simple Mail Transfer Protocol
SNA Systems Network Architecture
SNAP Sub-Network Access Protocol
SNI Subscriber-Network Interface
SNMP Simple Network Management Protocol
SNR Signal to Noise Ratio
SO Serving Office
SO/S Smart Omni-Orderwire Station
SOA Service Order Administration
SOH Section Overhead
SOHO Small Office/Home Office
SONET Synchronous Optical Network
SP SAR Sublayer Payload
SP Signaling Point
SPC Stored Program Control
SPCS Stored Program Control System
SPE Synchronous Payload Envelope
SPID Service Profile Identifier
SPRM Supplementary Performance Report Message
SPQR Senatus et Populus Qui Roma
SQR Signal to Quantizing noise Ratio
SRDM Sub Rate Data Multiplexer
SRL Singing Return Loss
SRM Signaling Route Management
SRP Spatial Reuse Protocol
SRTS Synchronous Residual Time Stamp
SS Supervisory Center
SS7 Signaling System No.7
SSCS Service Specific Convergence Sublayer
SSL Secure Socket Layer
SSP Service Switching Point
SSP SCCP Subsystem Prohibited
SSS SMDS Switching System
ST SAR Sublayer Trailer
STDM Statistical Time Division Multiplexer
STE Section Terminal Equipment
STP Signaling Trasfer Point
STM Synchronous Transfer Module
STP Shielded Twisted Pair
STP Signaling Transfer Point
STS Synchronous Transfer Signal
STS-1 Synchronous Transport Signal (level)-1
SU Signal Unit
SUERM Signaling Unit Error Rate Monitor
SVC Switched Virtual Call
SVC Switched Virtual Circuit
SVC Switched Virtual Connection
SWAP Shared Wireless Access Protocol
SWC Serving Wire Center
SWF Switched Fractional
SWF-DS1 Switched Fractional DS1
SYN Synchronization Character
SYNTRAN SYNchronous TRANsmission


T	Tip
TA Terminal Adapter
TAC Terminal Access Circuit
TACS Total Access Communications System
TALI Transport Adapter Layer Interface
TAP Test Access Path
TAPI Telephony Application Programming Interface
TASI Time Assigned Speech Interpolation
TAU Test Access Unit
TAU Time Assignment Unit
TC Terminating Channel
TC Transmission Convergence
TCA Threshold Crossing Alert
TCAP Transaction Capabilities Application Part
TCM Tandem Connection Maintenance
TCP Transmission Control Protocol
TCP Transport Control Protocol
TCP/IP Transmission Control Protocol/Internet Protocol
TDM Time Division Multiplexing
TDMA Time Division Multiple Access
TDR Time Domain Reflectometer
TE Terminal Equipment
TEI Terminal Endpoint Identifier
TELRIC Total Element Long-Run Incremental Cost
TFO Tandem Free Operation
TFTP Trivial File Transfer Protocol
THL Trans-Hybrid Loss
TL1 Transaction Language One
TLP Transmission Level Point
TLPU Telecommunications Line Protector Unit
TLWS Trunk and Line Work Station
TIMS Transmission Impairement Measuring Set
TIRKS Trunk Integrated Records Keeping System
TLP Transmission Level Point
TMC Time slot Management Channel
TMN Telecommunications Management Network
TN Telephone Number
TNS Transit Network Selection
TOH Transport Overhead
ToS Type of Service
TOS Testing Operation System
TPDU Transport Protocol Data Unit
TPI Tip-Party Identification
TRA Traffic Restart Allowed
TRU Transmit/Receive Unit
TRW Traffic Restart Waiting
TRX Tandem Repeater Exchange
TSC Test System Controller
TSDU Transport Service Data Unit
TSGR Transport System Generic Requirements
TSI Time Slot Interchange
TSID Test Signal Identification
TSR Terabit Switch Router
TTU Tandem T-1 Unit
TX Transmit


UA	Unnumbered Acknowledgement
UAS Unavailable Seconds
UCIC Unequipped Circuit Identification Code
UDC Universal Digital Channel
UDLC Universal Digital Loop Carrier
UDP User Datagram Protocol
UI Unit Interval
UI Unnumbered Information (frame)
UMTS Universal Mobile Telecommunications System
UNI User Network Interface
UNICODE UNIversal trunk-out-of-service Code
UPA User Part Available
UPC Usage Parameter Control
UPS Uninterruptible Power System
UPT User Part Test
UPU User Oart Unavailable
URL Uniform Resource Locator
URL Universal Resource Locator
USI User System Interface
USOC Universal Service Order Code
USOC Universal Service Ordering Code
UTP Universal Twisted Pair
UVG Universal Voice-grade Channel Unit


V(A)	Acknowledge state Variable
V(M) Recovery state Variable
V(R) Receive state Variable
V(S) Sent state Variable
VAZO Violating All-Zero Octet
VBR Variable Bit Rate
VC Virtual Channel
VC Virtual Circuit
VC Virtual Container
VCC Virtual Channel Connection
VCI Virtual Channel Identifier
VCL Virtual Channel Link
VDSL Very high bit rate Digital Subscriber Line
VDT Video Dial Tone
VG Voice Grade
VF Voice Frequency
VLAN Virtual Local Area Network
VLL Virtual Local Loop
VMWI Visual Message Waiting Indicator
VN Virtual Network
VNS Virtual Network System
VoATM Voice Over ATM
VoB Voice Over Broadband
VOD Video On Demand
VoDSL Voice Over DSL
VOFDM Vector Orthogonal Frequency Division Multiplexing
VoFR Voice Over Frame Relay
VoIP Voice Over Internet Protocol
VOP Voice Over Packet
VP Virtual Path
VPC Virtual Path Connection
VPI Virtual Path Identifier
VPLS Virtual Private LAN Service
VPN Virtual Private Network
VPRN Virtual Private Routed Network
VPT Virtual Path Terminator
VPX Virtual Path Cross-connect
VQC Vector Quantizing Code
VQC Voice Quantizing Code
VQL Vector Quantizing Level
VQL Variable Quantizing Level
VSAT Very Small Aperature Satellite
VSAT Voice over Satellite
VT Virtual Tributary
VXML Voice Extensible Markup Language


W-DCS	Wideband Digital Crossconnect System
WAN Wide Area Network
WAN PHY WAN Physical Layer
WAP Wireless Application Protocol
WATS Wide Area Telephone Service
WAW Wide Area Wireless
WDCX Wideband and Broadband Digital Cross-connect
WDM Wavelength Division Multiplexing
WECA Wireless Ethernet Compatibility Alliance
WEP Wired Equivalent Privacy
WFA Work Force Administration
WFQ Weighted Fair Queuing
WLAN Wireless Local Area Network
WML Wireless Markup Language
WPLAN Wireless personal Area Network


XA-FR	Exchange Access Frame Relay
XA-SMDS Exchange Access Switched Multi-megabit Data Service
XAME eXchange Access Mapping Entity
XC Crossconnect
XI X Identification (frame)
XID Exchange Identification
XML Extensible Markup Language
XO Extended Office




ZBTSI	Zero Byte Time Slot Interchange
ZCS Zero Code Suppression