The story goes that to do this, Friedhelm grabbed his trusty typewriter, sat down with a nice cup of tea and typed out a number of random sentences, and questions, on a sheet of paper to try and determine what the average number of characters used was.
After a number of tests, Friendhelm begun to see a pattern within his work. The majority of sentences he constructed fell in just under 160 characters.
Although this scientific test would fail dramatically under today's standards, Friendhelm was satisfied by his research and went forward to the committee to tell them of his findings.
Understandably unconvinced by his work, the committee disagreed with Friendhelm's methods, suggesting a text message would require almost double the characters set.
It's believed to calm the committee's fears, Friendhelm committed further 'research' into the matter.
He first took a bunch of postcards that he had received, collated the data and found that these postcards contained fewer than 150 characters. By this finding, he was actually being nice by offering users an additional 10 characters.
Secondly, Friedhelm analysed a number of messages sent through Telex (a telegraphy network for business professionals).
As Telex transmissions don't have a limit on the number of characters one can send, you'd be excused to think that 200, 300, 500-word messages were coming through.
In fact, Friendhelm found that on average the word volume within the messages being sent through Telex was roughly the same length as the messages received on the postcards.