Below is glossary of technical terms of network standards and protocols used in data communication, wireless communication for telecommunication including meanings of GSM, H.323, PBX - PCM, WAN, LAN, Routers, QOS, codecs, and MCUs.

GSM or GLOBAL SYSTEM FOR MOBILE COMMUNICATIONS is a digital cellphone technology that is based on TDMA (Time Division Multiple Access) and is predominantly used in European countries and it is also used in other countries of the world including India. GSM was developed in the 1980s and was distributed to be used in around 7 European countries in 1992. Nowadays, GSM is used in Asia, Europe, Australia, North America, and Chile. GSM operates on 1.9GHz PCS bands in USA and 900MHz and 1.8GHz bands in Europe. Global System for Mobile Communications defines the entire mobile system and is not just used as a radio interface but also TDMA and CDMA which is Code Division Multiple Access. In the year 2000, world had more than 250 million GSM users which represents more than half of world’s population of cellphone users. GSM use is increasing day by day due to its reliability and easy connectivity services. WAV and AIFF files are used for audio coding of the GSM standard used in IP telephony.

H.323 PROTOCOL is an overall recommendation that includes references to other network standards like H.225 and H.245 of ITU (International Telecommunication Union), which sets network standards for multimedia communications over packet-based networks that are not able to provide a guaranteed good Quality of Service (QoS).

H.323 PROTOCOL defines various entities, which make possible media and multimedia communications using endpoints, multipoint conferencing units or MCUs, gatekeepers, and gateways and their interaction.

PBX or PRIVATE BRANCH EXCHANGE is a specialized telephone system, which is used in both private and governmental organizations and companies to manage external and internal calls. Advantage of PBX is that the organization using it does not requires a different phone line for each of their phones and internal calls do not go outside and are not billed.

PULSE CODE MODULATION or PCM converts sound or voice analog signals into digital signals, so that these signals can be processed easily by a digital device, for example, a computer. You also need to use a codec if you want to compress the results for transmissions to occupy lowest possible bandwidth.

ROUTER is a complex program running on a computer, a physical device, which forwards data packets over a WAN or LAN to another. Based on routing protocols, a router reads destination network addresses of each packet, which arrives to its server and then decides on sending them via the best route possible which is based on cost, traffic load, speed, and other factors. Routers usually work at third level of protocol stack, while switches and bridges work at second level of protocol stack.

VOICE OVER ATM enables a router to carry calls and faxes and other voice traffic over an Asynchronous Transfer Mode network. Voice traffic over Asynchronous Transfer Mode network is encapsulated via a special method for multiplexed voice.

WIDE AREA NETWORK or WAN communications network is used to connect computers and other communication devices using public or private connections.