Since the telephone was invented by Scotland’s Alexander Graham Bell in 1876, telephony has evolved immeasurably, with the intervening decades marked by continual improvements in technology to the current point where smartphones are abundant in all parts of the world.

When telephone exchanges were first set up in the late 19^th century, people had to manually connect wires to one another through a central station and the technology was used primarily by professionals such as doctors and police officers. New ground was broken in 1900 with the first international phone call from USA to Cuba, with the first transatlantic call taking place a quarter of a century later, around the same time that rotary phones were becoming commonplace.

Developments in telephony continued into the middle of the 20^th century with the introduction of area codes and touch-tone dialling. In the 1980s, the first mobile phones were launched, although at a cost of almost $4,000, their usage was restricted to wealthier business people.

The launch of the Internet a decade later brought telephony to a hugely exciting new place. Voice over Internet Protocol (VoIP) enabled Internet users to call one another online if they both had speakers and a microphone, and in 2003 the revolutionary Skype was founded.

From the early days of manual connections and exclusivity of usage, business telephony is now very much an open door that is instantly accessible the world over. This infographic by Irish Telecom charts the key stages in the development of telephony over the past 140 years.