On Friday, twenty years ago, a telephonic call between two Finnish personalities heralded a mobile technology that has since then transformed the way people communicate worldwide. Today, Global System for Mobile Communications, popularly known as GSM, is the dominant technology utilised for mobile telephony.

With increased mobile penetration as well as availability of different kinds of handsets, the use of GSM is growing by the day compared to competing CDMA technology, experts said. Going by estimates, GSM has captured over 80 per cent of the global mobile phone market in a span of 20 years.

In India, a majority of the 800 million mobile phone customers are using handsets based on GSM technology.

airtel, Vodafone and Idea are among the prominent GSM service providers. Even players such as Tata Teleservices and Reliance Communications, which started as CDMA operators, today offer both technologies.

GSM technology helps in offering high-quality voice calls and services such as text messaging (SMS).

Reports suggest that there are 838 GSM operators worldwide, catering to over 4.2 billion subscribers. GSM operators are estimated to have raked in about USD 500 billion in annual revenues in 2009.

GSM is today available in 234 countries and independent territories around the globe.

The first GSM network was built by Telenokia and Siemens - today's Nokia Siemens Networks - for the Finnish operator Radiolinja, now operating under the name Elisa.

The world's first GSM call on a commercial network was made on July 1, 1991, between Finland's former prime minister Harri Holkeri and vice mayor of the city of Tampere Kaarina Suonio.

During the call, Holkeri and Suonio discussed the benefits of the new digital GSM technology, including superior voice quality and security, and the fact that the phone's identity is in the SIM card, making it easy for consumers to choose the product they like.

In India, the first mobile phone call was made on a Nokia phone on a Nokia network (now Nokia Siemens Networks) on July 31, 1995.

Developed as a replacement for first generation analog cellular networks, the GSM standard was adopted in 1987 as the European standard for digital mobile technology. This second generation mobile technology could carry data as well as voice traffic.