Why is the keypad arrangement different for a telephone and a calculator?
It is jolly left over that a estimator and a trace - pure tone telephony have exactly opposite layouts for their keypad , which have many identical component . The reasons behind the differences are not known for certain , but a few theories survive . The first hypothesis deals with the telephone ’s circuitry and tone - recognition hardware . When the touch - tonetelephonewas being design in the late 1950s , the calculator and adding - auto house decorator had already established a layout that had 7 , 8 and 9 across the top row ....