How do mobile phones send texts?

Computers work with numbers not letters. They were invented as calculating machines and were used for 'number crunching’.  Early computers were used to break numeric codes during the Second World War.

Photograph of Colossus, the first digital programmable computing device.

Colossus - the first electronic digital programmable computing device

By the 1960s, typical users were the Utility Companies who employed hundreds of people to process bills and accounts. Computerisation of these processes saved large sums of money - but also led to amusing errors, such as million pound gas bills!

As early as 1960 people were also looking at using computers for communication, and were working on trying to computerise the Telegraph Code. Messages had been sent over long distances by telegraphy and wireless using the Morse Code. The hope was that this process couild also be computerised.

In 1963 the first edition of a new code was published in America. It was called the ASCII standard, the acronym for “American Standard Code for Information Exchange”. 

Table showing the ascii set in which each number from 0 to 127 represents a letter or character.

The ASCII standard assigns a letter, number or control character to each of the numbers from 0 to 127 (= 128 characters, the maximum possible on an early eight bit computer).

All computers built after that date contained the ASCII code set and that included mobile telephones, because they are *computers.

When you press the keys on a mobile phone, the numbers from 0 to 9 are transmitted digitally using wireless technology. By pressing the same key more than once in quick succession, early phones could transmit an ASCII number. It could be used to assign a name to a phone number and was an useful convenience.

But the ability to built up actual words meant that you could also send short text messages to someone who also had a mobile phone. It never occurred to adults to do this, probably because their mindset was locked to the idea of “telephone = voice conversation”.

Teenagers, on the other hand, are not blinkered by tradition and experience and they were quick to spot a new opportunity. They began to exchange texts with their friends.

Next: The End of the Job?

Find out more and see the ASCII Table more clearly in Wikipedia
See a more detailed history of the ASCII set

(both open in a new window)

* Footnote: I’m not certain if the early, analogue, cell phones could send texts. If you know please get in touch. Drop me a line using my contact page.

© Brian Smith 2015