W hen you make a call on your mobile phone today, tip your hat to Amos E. Joel Jr, the American electrical engineer who patented the idea of a cellular phone system in 1972 and who has died at the age of 90. It was he who invented the electronic switching device that allowed phone users to move from one "cell area" to another without losing their connection.

Although another American, Martin Cooper, is widely credited with "inventing" the mobile phone for Motorola in 1973, his first wireless handset relied on a single base tower, linked up with the landline system, and had limited range. Wireless phones would eventually work "on the move" as a result of the technology detailed in Joel's invention of the previous year, US patent number 3,663,762, titled "Mobile Communication System".