Backscatter
The History of the Trefoil
Instantly recognisable to all our readers – but how many know its history ? Back in 1946 , the symbol was first ' doodled ' by members of a research group at the Berkeley Radiation Laboratory , University of California who were looking for an image that , as one of the group described in a letter , “ would best symbolize the degree of hazard , type of activity , etc . but which was simple in design ”. The final design “ was supposed to represent activity radiating from an atom ”.
In 1948 , the symbol began wider use when Brookhaven National Laboratory requested a “ standardised symbol of standardised colours ” for use in its radiation safety programme . Surprisingly , the first designs weren ' t the black and yellow that we are so familiar with . In fact , the choice of colours was of greater discussion than the symbol itself , with the original design having magenta blades on a blue background . Blue was chosen because it was an uncommon colour in radiation controlled areas ; however , it was felt that most people did not associate blue with danger and it faded , especially outdoors . The magenta symbols were cut out and stapled on cards of different colours , and at a distance of 20 feet , a committee selected the magenta on yellow as the best combination .
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Lesser-known uses of Radiation – The Cash Dispenser
The world ' s first Automated Teller Machine ( ATM ) was installed in a branch of Barclays in Enfield , north London , in 1967 .
John Sheppard-Barron led the team credited with the invention . He conceived the idea for a self-service machine dispensing cash whilst lying in the bath . He was considering the problem of bank opening hours , having turned up at a bank after closing time one day and found himself unable to withdraw money . “ It struck me there must be a way I could get my own money , anywhere in the world . I hit upon the idea of a chocolate bar dispenser , but replacing chocolate with cash .”
Plastic cards hadn ' t been invented , so the new machine used cheques that were impregnated with carbon-14 . The machine detected it , then matched the cheque against a pin number . However , Mr Shepherd-Barron denied there were any health concerns : “ I later worked out you would have to eat 136,000 such cheques for it to have any effect on you .”
The machine paid out a maximum of £ 10 a time . “ But that was regarded then as quite enough for a wild weekend ,” he said .
1946 Today ( US ) Today ( International )
Evolution of the symbol In the early 1950s , different modifications of the design were developed , for example , with straight or wavy arrows between or within the blades . By the late 1950s , the American National Standards Institute ( ANSI ) had codified the official version — magenta on yellow . In the UK and other countries , the black on yellow symbol is used .
Radiation Protection Today Spring 2024 37