On 3 April 1973, Marty Cooper stood on a corner of Sixth Avenue in New York and took a phone book from his pocket.

He then punched a number into a large, cream-coloured device and put it to his ear while passers-by stared at him.

Mr Cooper, an engineer at Motorola, rang his counterpart at rival firm Bell Laboratories, to triumphantly tell him he was calling from "a personal, handheld, portable cell phone".

He recalls there being silence on the end of the line. "I think he was gritting his teeth," says the 94-year-old, laughing.

Bell Laboratories had been focusing on developing a car-based phone instead, he says. "Could you believe that? So we had been trapped in our homes and offices by this copper wire for over 100 years - and now they were going to trap us in our cars!"

Needless to say, Mr Cooper and Motorola did not agree this was the way forward - and history has proved them right.

The basics of how that first call worked haven't changed much. The phone converts your voice into an electric signal, which modulates a radio wave. The radio wave goes to a mast; the mast sends your voice to the person you are calling, and by reversing the process, that person can then hear you speak.

The commercial version of Marty Cooper's prototype, the Motorola Dynatac 8000X, was released 11 years after that first call, in 1984. It would cost the equivalent of 9,500 ($11,700) if bought today, says Ben Wood, who runs the Mobile Phone Museum.

"Basically, it was just dial the number and make the call," Mr Wood explains. "There was no messaging, no camera. Thirty minutes of talk-time, 10 hours to charge the battery, about 12 hours of stand-by time and a 6in (15cm) antenna on the top."

It also weighed 790g (1.7lb) - nearly four times the weight of the iPhone 14, at 172g.

BBC News