Basic GSM abbreviations
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AAL - ATM Adaptation Layer
A-bis = Interface between the BSC and BTS in a GSM network
AB - Access Burst
used for random access and characterised by a longer guard period to allow for burst
transmission from a MS that does not know the correct timing advance when first contacting a
network
ABR - Available Bit Rate
AC - Alternating Current ( the standard electricity type )
ACCH - Analog Control Channel
ACTS - Advanced Communications Technologies and Services.
a European technology initiative
ACU - Antenna Combining Unit
AC Charger :
an accessory device that allows you to power and/or charge your phone from a wall outlet
ADC - Analog to Digital Converter
Advice of charge:
A service which provides the user with information on the cost of calls from a mobile phone
AFC - Automatic Frequency Control
AGC - Automatic Gain Control
AGCH - Access Grant Channel; downlink only, BTS allocates a TCH or SDCCH to the MS,
allowing it access to the network
A-interface :
Interface between the MSC and BSS in a GSM network
AM - Amplitude Modulation
AMPS - Advanced Mobile Phone Service
Advanced Mobile Phone System (AMPS) is the analog mobile phone system standard
developed by Bell Labs, and officially introduced in the Americas in 1983[1][2] It was the primary
analog mobile phone system in North America (and other locales) through the 1980s and into
the 2000s, and is still widely available today, although use has dropped considerably with the
introduction of various digital standards.
Total Access Communication System (TACS) and ETACS are mostly-obsolete variants of
AMPS which were used in some European countries (including the UK). TACS was also used in
Japan under the name Japanese Total Access Communication (JTAC).[3][4]
AMR - Adaptive Multi-Rate codec.
Developed in 1999 for use in GSM networks, the AMRhas been adopted by 3GPP for 3G
Analogue:
The representation of information by a continuously variable physical quantity such as voltage
Antenna:
a part of a cell phone that receives and transmits cellular radio-frequency transmissions
ASCII
American Standard Code for Information Interchange
ASIC - Application Specific Integrated Circuit
Electronic chips designed for some concrete purposes (for example, in phone it controlls
communication between MCU and DSP) They're designed and produced by the companies
which use them.
ATM
Asynchronous Transfer Mode; a multiplexed information transfer and switching method in which
the data is organised into fixed length 53-octet cells and transmitted according to each
application’s instantaneous need
AVCH - Analog Voice Channel
BB5 - base band 5
BCC - Base-station Color Code
B-CDMA - Broadband Code Division Multiple Access
BCH - Broadcast Channels( carry only downlink information and are mainly responsible for
synchronisation and frequency correction (BCCH, FCCH and SCH)
BCCH - Brodcast Control Channel
the logical channel used in cellular networks to broadcast signalling and control information to
all mobile phones within the network
BGA - ball grid array
B-ISDN - Broadband ISDN
BPS - Bits Per Second
( a measure of how fast binary digits can be sent through a channel. The number of 0s and 1s
that travel down the channel per second.)
Base transceiver Station Identity Code
BTS - Base Transceiver Station
(This device allows communication between phones and cellular network or it is the network
entity which communicates with the mobile station)
Back -light Illumination
illuminates a wireless device’s display and keypad for better low light viewing
Band :
a specific range of frequencies in the radio frequency (RF) spectrum.
Battery:
A chargeable device which provides the mobile phone with power. A variety of battery
technologies have been used for mobile phones including nickel cadmiu(NiCad),nickel metal
hydride (NiMH) and lithium ion (Li-ion)
Battery status/Battery charge display
An indication of the amount of battery life remaining
Battery Capacity the capacity of wireless devices’ battery. Measured in milliampere hours
(mAh).
Call barring
A service which enables users to bar certain incoming or outgoing calls on their mobile phones
Call timer:
A service which keeps track of the amount of airtime being used by the subscriber on a
cumulative basis
Call divert:
The capability to divert incoming calls to another phone (fixed or mobile) or to an answering
service
Call hold:
The ability to put an ongoing call on hold whilst answering or making a second call
Caller ID:
Caller Identification (displays the name/number of the person calling a mobile phone. Also
known as CLI)
CB - Cell Broadcast
CCCH - Common Control Channels; a group of uplink and downlink channels between the MS
and the BTS (see PCH, AGCH and RACH)
CCONT- Current Controller (in nokia fones)
CDMA - Code Division Multiple Access
(Code Division Multiple Access; also known as spread spectrum (or IS-95), CDMA cellular
systems utilise a single frequency band for all traffic, differentiating the individual transmissions
by assigning them unique codes before transmission. There are a number of variants of CDMA
(see W-CDMA, B-CDMA, TD-SCDMA et al)
Cell:
The area covered by a cellular base station. A cell site may sectorise its antennas to service
several cells from one locationCell site
The facility housing the transmitters/receivers, the antennas and associated equipment
Cell Site:
a fixed cellular tower and radio antenna that handles communication with subscribers in a
particular area or cell. A cellular network is made up of many cell sites, all connected back to the
wired phone system.
CF - Call Forwarding
CI - Carrier to Interference ratio
CID - Caller Identification
Circuit switching:
A method used in telecommunications where a temporary dedicated circuit of constant
bandwidth is established between two distant endpoints in a network. Mainly used for voice
traffic; the opposite of packet switching
CNT- Content
COBBA- Common Baseband Analog
CPU - Central Processing Unit
CMOS - Complementary Metal Oxide Substrate
Codec:
A word formed by combining coder and decoder the codec is a device which encodes and
decodes signals. The voice codec in a cellular network converts voice signals into and back
from bit strings. In GSM networks, in addition to the standard voice codec, it is possible to
implement Half Rate (HR) codecs and Enhanced Full Rate (EFR) codecs
Control signal:
A signal sent to a cellular phone from a base station or vice versa which carries information
essential to the call but not including the audio portion of a conversation
CRC - Cyclic Redundancy Check
CT - Cordless Telephony
CTA - Cordless Terminal Adaptor (a DECT term)
CTM - Cordless Terminal Mobility
CTR - Common Technical Regulation
CUG - Closed User Group
D/A - Digital to Analogue conversion
DAC - Digital to Analogue Convertor
D-AMPS - Digital AMPS, a US wireless standard also known as IS-136
Data capable:
Mobile phones which have the capability to enable transmission of data from a laptop computer
or PDA via the phone
Datacable : interface for conecting a mobile fone to pc
db - decibel (unit if sound)
DCT /3,4 - digital core technology
DCT/L - digital core technology linda
DCCH - Digital Control Channel
DTCH - Digital Traffic Channel
DTX - Discontinous Transmission Exchange
DCA - Dynamic Channel Assignment
DCCH - Dedicated Control Channels
( responsible for roaming, handovers, encryption etc)
DCE - Data Communications Equipment
DCH - Data Clearing House
DCS1800 - Digital Cellular System at 1800MHz, now known as GSM1800
Digital:
a method of representing information as numbers with discrete values; usually expressed as a
sequence of bits
Digital a method of encoding a transmission that involves translating information (in the case of
digital phones the information would be a voice conversation) into a series of 0’s and 1’s. Digital
communications technology offers cleaner calls without the static and distortion that is common
with analog phones. The majority of new handsets sold today are digital rather than analog
technology.
DSP - Digital Signal Processor
Digital Signal Processing refers to manipulating analog information, such as sound or
photographs that has been converted into a digital form to improve accuracy and reliability of
digital communications.
DSC- Digital Signal Controller
DTE - Data Terminal Equipment
DTMF - Dual Tone MultiFrequency;
(better know as Touch Tone. The tones generated by touching the keys on the phone are used
for a variety of purposes )
DTX - Discontinuous Transmission
Dual Band:
The capability of GSM infrastructure elements and handsets to work across both the 900MHz
and 1800MHz bands. The capability to seamlessly handover between the two bands offers
operators major capacity gains
Duplex:
The wireless technique where one frequency band is used for traffic from the network to the
subscriber (the downlink) and another, widely separated, band is used for traffic from the
subscriber to the network (the uplink)
EEPROM - Electrically Erasable Programmable Read Only Memory
EFR- Enhanced Full Rate
(Enhanced Full Rate (codec): an improved version of the standard voice codec used in GSM
phones; offers improved speech quality without impacting on network capacity)
EFT - Electronic Funds Transfer
EGSM - Extended (frequency range) GSM
EIR - Equipment Identity Register (a database that contains a list of all valid mobile stations
within a network based on their IMEI)
EIRP - Effective Isotropic Radiated Power
EPOC :
The mobile phone operating system developed by Symbian. Derived from epoch-the beginning
of an era-EPOC is a 32-bit operating environment which comprises a suite of applications,
customisable user interfaces, connectivity options and a range of development tools
EPROM - Erasable Programmable Read Only Memory
ESMR - Enhanced Special Mobile Radio; a US PMR variant (see SMR)
ESN - Electronic Serial Number; a 32-bit number that uniquely identifies a mobile phone
FB - Frequency Correction Burst; used for frequency synchronisation of the mobile
FDD - Frequency Division Duplex
FOMA - Freedom Of Mobile multimedia Access
Gbit/s:
A unit of data transmission rate equal to one billion bits per second
GMSC - Gateway Mobile Services Switching Centre; the gateway between two networks
GCF - Global Certification Forum
Geostationary:
Refers to a satellite in equatorial orbit above the earth which appears from the surface to be
stationary
GERAN - GSM-EDGE Radio Access Network the name for the evolution of GSM towards 3G
based on EDGE
GGRF - GSM Global Roaming Forum
GGSN - Gateway GPRS Support Node; the gateway between a cellular network and a IP
network.
GHz:
A unit of frequency equal to one billion Hertz per second
GMPCS - Global Mobile Personal Communications by Satellite
GMSK - Gaussian filtered Minimum Shift Keying
GPRS:
General Packet Radio Service (GPRS) is a mobile data service available to users of GSM and
IS-136 mobile phones. GPRS data transfer is typically charged per megabyte of transferred
data, while data communication via traditional circuit switching is billed per minute of connection
time, independently of if the user actually has transferred data or been in an idle state. GPRS
can be utilized for services such as WAP access, SMS and MMS, but also for Internet
communication services such as email and web access. In the future, it is expected that low
cost voice over IP will be made available in cell phones.
GPS:
The Global Positioning System (GPS), is currently the only fully-functional satellite navigation
system. More than two dozen GPS satellites are in medium Earth orbit, transmitting signals
allowing GPS receivers to determine the receiver's location, speed and direction.
GRX - GPRS Roaming Exchange
GSM
The Global System for Mobile Communications, GSM (original acronym: Groupe Spécial
Mobile) is the most popular standard for mobile phones in the world. GSM service is used by
over 2 billion people across more than 212 countries and territories.[1][2] The ubiquity of the
GSM standard makes international roaming very common between mobile phone operators,
enabling subscribers to use their phones in many parts of the world. GSM differs significantly
from its predecessors in that both signaling and speech channels are Digital call quality, which
means that it is considered a second generation (2G) mobile phone system. This fact has also
meant that data communication was built into the system from the 3rd Generation Partnership
Project (3GPP).
Hands-free:
The operation of a cellular phone without using the handset; usually installed in vehicles.
Handoff:
The transfer of control of a cellular phone call in progress from one cell to another, without any
discontinuity
HR - Half Rate Traffic
IC - Intergrated Circuit
ICSP - In Circuit Serial Programming
IF- Intermediate Frequency
Infrared data port:
A facility on a mobile phone to allow information to be exchanged with other devices e.g. a PC
using infra red technology
Internet
The Internet is the worldwide, publicly accessible network of interconnected computer networks
that transmit data by packet switching using the standard Internet Protocol (IP). It is a "network
of networks" that consists of millions of smaller domestic, academic, business, and government
networks, which together carry various information and services, such as electronic mail, online
chat, file transfer, and the interlinked Web pages and other documents of the World Wide Web.
IMEI - International Mobile Equipment Identity
The International Mobile Equipment Identity (IMEI) is a number unique to every GSM and UMTS
mobile phone. It is usually found printed on the phone underneath the battery and can also be
found by dialing the sequence *#06# into the phone.
The IMEI number is used by the GSM network to identify valid devices and therefore can be
used to stop a stolen phone from accessing the network. For example, if a mobile phone is
stolen, the owner can call his or her network provider and instruct them to "ban" the phone using
its IMEI number. This renders the phone useless, regardless of whether the phone's SIM is
changed.
I-mode:
A service developed by Japanese operator NTT DoCoMo, I-mode delivers a huge range of
services to subscribers and has proved enormously popular with some 30 million regular users.
The revenue sharing model used for I-mode is being adopted by other operators as the basis for
the new services enabled by GPRS and 3G
IMSI - International Mobile Subscriber Identity
(an internal subscriber identity used only by the network)
IP - Internet Protocol
IrDA - Infra red Data Association
Iridium:
A low earth orbit satellite communications system developed initially by Motorola.
ISDN - Integrated Services Digital Network
ISO
International Standards Organisation
ISP - Internet Service Provider
iTAP:
software developed by Motorola and built into some wireless phones and PDAs that makes
typing words on a keypad easier. The competitor to iTAP is T9
JAF - Just Another Flasher
Java:
A programming language developed by Sun Microsystems Java is characterised by the fact that
programs written in Java do not rely on an operating system
JPEG- Joint Photographic Experts Group
JTAG - Joint Test Action Group
Kbps : Kilobits Per Second, a measure of bandwidth
LAN
Local Area Network
LANS
Local Area Network Services
LED - Light Emitting Diode
(a semiconductor device that illuminates when electricity passes through it. Often used as an
indicator light, or to spell out words and numbers. LEDs come in many colors, and some LEDs
contain multiple elements and are therefore capable of multiple colors. Provides good visibility in
direct sunlight and in darkness)
LPT - Line Print Terminal
LMSS
Land Mobile Satellite Service
Lock
A function on a cellular phone which, when activated, prevents use of the phone until the user
enters a security code
LCD - Liquid crystal display
Lithium Ion battery:
a type of rechargeable battery for cell phones which is generally lighter weight than earlier
battery types, has a relatively longer cycle life, and generally does not suffer from “memory”
effect.
MAC - Media Access Control; the lower sublayer of the OSI system
MAD - Memory Analog Digital
MAP - Mobile Application Part
Mb- Megabite
( a unit of data transmission speed equal to one million bits per second)
MCC - Mobile Country Code
MCU - Micro Control Unit
MCPA - Multi Carrier Power Amplifier
MHz - Megahertz (a unit of frequency equal to one million Hertz)
MMI - Man Machine Interface
MMS - Multimedia Messaging Service
(an evolution of SMS, MMS goes beyond text messaging offering various kinds of multimedia
content including images, audio and video clips)
Modulation:
The process of imposing an information signal on a carrier. This can be done by changing the
amplitude (AM), the frequency (FM) or the phase, or any combination of these
MPEG:
Motion Picture Experts Group; MPEG4 is a technology for compressing voice and video so that
the information can be transmitted over normally difficult links such as mobile radio
MS - Mobile Station
MSIN - Mobile Station Identification Number
MSISDN - Mobile Station International ISDN Number
MSK - Minimum Shift Keying (Another term for FFSK)
Multiplexing:
A telecommunications technique where several channels can be combined to share the same
transmission medium. The most common forms are Time Division Multiplexing (TDM) and
Frequency Division Multiplexing (FDM)
Master Reset:
restores the setting to factory
MIDI - Musical Instrument Digital Interface
(a standard that allows digital musical instruments to communicate with one another. In cell
phone terms, MIDI is what gives you polyphonic sounds; which means your ring tones can
sound like real music instead of beeps. )
MMS - Multimedia Messaging Service
(a further extension of SMS and EMS.MMS is designed to make use of newer and quicker
mobile transmission methods such as GPRS, HSCSD, EDGE and UMTS, involving the
attachment of multimedia extensions to messages, such as video and sound. An e-mail function
is also planned. )
MO-SMS - Mobile-Originated Short Message Service
(the ability to send short text messages from a phone. Both the phone and the carrier’s network
must support this feature for it to work. Messages can be sent to other phones by phone
number. Many phones also allow sending messages directly to e-mail addresses. )
NCC (National Color Code or Network Color Code
NET
Norme Europeenne de Telecommunications
NMSI - National Mobile Subscriber Identity
No Service:
An indication on the display of a cellular phone that indicates that the user is in an area where
cellular service is unavailable
OMAP - Open Multimedia Applications Platform
OTP - One Time Programable
PCM
Pulse Code Modulation; the standard digital voice format at 64kbit/s
PCMCIA
Personal Computer Memory Card Interface Association the body responsible for defining
the standards and formats for memory expansion cards for laptop computers and PDAs. Now
extended to cover cards for mobile phones
PCU
Packet Control Unit; an element in a GPRS/UMTS network
PDA
Personal Digital Assistant
PIN
Personal Identifier Number
PSU
Power Supply Unit
PCN
Personal Communications Networks; an outdated term for GSM services in the 1800MHz band
PDA
Personal Digital Assistant; a sophisticated handheld device with advanced display
facilities and a range of business-oriented software programs
Phone book
A list of personal names and numbers stored in a mobile phone’s internal memory or in
the SIM card. These numbers can be called by accessing the appropriate memory and
making a single key stroke
PIN
Personal Identity Number; a number, usually four digits, that must be keyed into a
mobile phone to make it work. A security measure to prevent unauthorised usage
P-Java (Personal Java) a Java API and specification for running Java applications on
small devices.
Packet a piece of data transmitted over a packet-switching network such as the Internet
or wireless Internet; a packet includes not just data but also its destination.
Packet Switching a type of communication that splits information into “packets” of data
for transmission. This is efficient, as it only uses radio spectrum when it’s actually
sending something, rather than keeping an open channel at all times (as is done in
circuit switching). Packet switching is a core component to 3G technology.
Passive Matrix Display an LCD technology that uses a grid to supply the charge to each
particular pixel on the display. An STN screen has a slower refresh rate than a TFT
screen, but it’s cheaper. Also called a SuperTwist Nematic of STN display.
PC Card (PCMCIA) a removable, credit-card sized devices that may be plugged into slots
in PCS and wireless communication devices to provide fax or modem functions or network
cards.
PCMCIA (Personal Computer Memory Card International Association) a group of hardware
manufacturers and vendors responsible for developing standards for PC Cards (also
called PCMCIA cards.)
PCN:
also known as DCS 1800 or GSM 1800, PCN is a term used to describe a wireless
communication technology in Europe and Asia.
PDA (personal digital assistant) a portable, handheld computing device that acts as an
electronic organizer. PDAs are typically used for managing addresses, appointments,
to-do lists and notes, but some newer models support wireless Internet access, e-mail,
and other interactive applications. Also referred to as Handheld Computers. PDAs come
in two major flavors - Palm and Pocket PC.
PIN (Personal Identification Number) a numeric code or password that may be required by
a service provider in order to make outgoing calls or obtain access to certain
applications and data. This code is always associated to a SIM card, not a phone and is
designed to help guard against cellular fraud.
PTT (Push-To-Talk) a two-way communication service that works like a “walkie talkie”.
This feature, found on Motorola iDEN phones from Nextel and Telus Mobility’s Mike,
allow communication in only direction at a time unlike a cell phone that allows for
simultaneous conversations. New PTT systems are now being introduced that use VoIP
technology to provide PTT service digitally over 3G data networks
PUK (Personal Unblocking Code) used to unblock a blocked SIM card, this code is given
during the sub******ion of a phone
PWR:
represents the on/off (power) key on some wireless devices.
RAM - Random Access Memory
RAP3G- Radio Application Processor 3rd Generations
Reuse:
The assignment of frequencies or channels to cells so that adjoining cells do not use the same
frequencies and cause interference whereas more distant cells can use the same frequencies.
Reuse expands the capacity of a cellular network by enabling the use of the same channels
throughout the network
RF AMP = Radio Frequency Amplifier
RFP - Radio Fixed Part
(equivalent to a base station in a DECT system)
RP - Radio Part
Roaming:
A service unique to GSM which enables a subscriber to make and receive calls when outside
the service area of his home network e.g. when travelling abroad
Router:
A device which forwards information in a network on a connectionless basis
RT - Remote Terminal
RX :- signal received
SAR - Specific Absorption Rate
S-CDMA - Synchronous CDMA (see CDMA)
SCH - Synchronisation Channel
(downlink only frame synchronisation and identification of base station)
SCP - Switching/Service Control Point
SDCCH - Stand-alone Dedicated Control Channel; communications channel between the MS
and the BTS. Used for signalling during call set-up before a TCH is allocated
Security Code:
a numeric code (password) used to prevent unauthorized or accidental alteration of data
programmed into wireless phones. The security code can be used by the owner of a phone to
change the lock code.
SIM - Subscriber Identity Module
A smart card containing the telephone number of the subscriber, encoded network identification
details, the PIN and other user data such as the phone book. A user’s SIM card can be moved
from phone to phone as it contains all the key information required to activate the phone
Streaming:
An Internet derived expression for the one-way transmission of video and audio content
Smartphone:
a combination of mobile phone and personal digital assistant
SMS - Short Message Service
(a text message service which enables users to send short messages (160 characters) to other
users. A very popular service, particularly amongst young people, with 400 billion SMS
messages sent worldwide in 2002)
SP - Service Provider
SRAM - Syncronous Random Access Memory
Standby time:
The length of time a battery can power a mobile phone when it is switched on but not making or
receiving calls
Symbian:
A company created by Psion, Nokia, Ericsson and Motorola in 1998 with the aim of developing
and standardising an operating system which enable mobile phones from different
manufacturers to exchange information
The operating system is known as EPOC. Matsua has subsequently joined Symbian
TACS - Total Access Communications System
TAP - Transferred Account Procedure
(the essential charging methodology for international GSM roaming. There have been four TAP
standards, TAP1, TAP2, TAP2+ and TAP3. The latter offers variable record length and is
sufficiently flexible to support all future requirements arising from the move to 3G)
TFD : Thin Film Diode
(a type of LCD (Liquid Crystal Display) flat-panel display technology. TFD technology combines
the excellent image quality and fast response times of TFT, with the low power consumption
and low cost of STN.)
TFT - Thin Film Transistor
(an LCD technology that uses transistors to precisely control the voltage to each liquid crystal
cell. This is also referred to as an “active matrix” display. TFT screens offer the best image
quality and refresh rates, but at a higher cost.)
Tri-band:
Refers to a mobile phone able to operate on the three internationally designated GSM
frequencies- 900, 1800 and 1900MHz
TRX:
Transmitter/receiver (transceiver)
Total Access Communications System (an AMPS variant deployed in a number of countries
principally the UK)
Talk-time:
The length of time a battery can power a mobile phone when making or receiving calls
T9 :
software built into some wireless phones and PDAs that makes typing words on a keypad
easier. The competitor to T9 is iTAP
Tri-Band fone:
a phone capable of operating on three different digital frequencies (example: 900MHz,
1800MHz and 1900MHz).
U
Upp - Universal power processor
UI - User Interface
UMTS - Universal Mobile Telecommunications System
(the European entrant for 3G; now subsumed into the IMT-2000 family as the WCDMA
technology.)
UPN - Universal Personal Number
URL - Uniform Resource Locator( the addressing system of the Internet)
UTRA - Universal Terrestrial Radio Access
USIM - Universal Subscriber Identity Module; the 3G equivalent of the GSM SIM
UWB - Ultra Wide Band
USB - Universal Serial Bus
VBR - Variable Bit Rate
VCO - Voltage Control Oscillator
VHE - Virtual Home Environment
VLR - Visitor Location Register
Vocoder - Voice coder
VoIP - Voice over Internet Protocol
VPN - Virtual Private Network
VSAT - Very Small Aperture Terminal
VSELP - Vector Sum Excited Linear Prediction
VSLI- Very Large Scale Integration
Voicemail:
A service offered by network operators whereby calls received when the mobile is in use,
switched off or out of coverage can be diverted to an answering service which can be
personalised by the user
WAP - Wireless Application Protocol
(Wireless Application Protocol; a de facto standard for enabling mobile phones to access the
Internet and advanced services. Users can access websites and pages which have been
converted by the use of WML into stripped-down versions of the original more suitable for the
limited display capabilities of mobile phones)
WASP - Wireless Application Service Provider
Web clipping:
this is an application that allows a user to extract relevant information from a web page for
display on a smart phone or a PDA.
Wi-Fi Wireless Fidelity, the popular term for the 802.11b wireless Ethernet standard.
Windows CE:
a streamlined version of Windows from Microsoft for handheld computers which has since been
upgraded and renamed Pocket PC. Windows CE run Pocket versions of Microsoft office
applications such as Word and Excel as well as many applications that were geared specifically
for the smaller platform.
WLAN - Wireless Local Area Network
a short range radio network normally deployed in traffic hotspots such as airport lounges, hotels
and restaurants. WLAN enables suitably equipped users to access the fixed network wirelessly,
providing high speed access (up to 11Mbit/s download) to distant servers. The key WLAN
technologies are the IEEE802.11 family and ETSI HIPERLAN/2