At the touch of a button

MOBILE PHONE ‘ CALL’ BUTTON

Not many people are familiar with Laila Ohlgren. But billions of people use her innovation every day when they press the green button on their mobile phone to make a call.

For most people – particularly younger folks – it’s natural to dial a phone number first and then press the ‘call’ button. But that’s not how things worked with old-fashioned landline phones. In those days, you had to pick up the receiver (shaped like the symbol on the green button) to get a line and then use the buttons or rotary dial to input a sequence of digits to call another telephone.

Those steps were also used on the first mobile telephones on the market in the 1980s. But early mobile networks had patchy coverage and often suffered outages, especially if you were on the move. There was a high risk of losing a connection or losing numbers when dialling.

This is where Laila Ohlgren, the first female engineer at the Swedish state telephone authority, comes in. She joined the authority in 1956 at the age of 19 and obtained an engineering degree later on. In the late 1970s she was working on NMT, the Nordic mobile telephony project. It was one of the world’s first wireless telephone networks.

Shortly before the launch of NMT in 1981, she hit upon a solution to the dialling problem with mobile phones. Instead of transmitting the digits one by one, you could incorporate a button that would send the entire telephone number that had been dialled all at once. That eliminated the danger that the signal for any digit would be lost in a mobile black spot.

In 2009, Laila Ohlgren was awarded the Polhem Prize, Sweden’s most prestigious award for engineering. She died in 2014 at the age of 76. By that time, her green button had been a standard feature on mobile phones all over the world for 30 years.

The green button is one of the simplest and yet most significant innovations for mobile phones.