The selection of a single standard design for the location of the buttons on the phone manufacturers of vehicles and companies involved in the provision of communications was conceived in the late 50-ies. The determining factor in this question was the study of the American company AT&T, which was published in the journal Bell Systems Technical Journal in 1960. It can be fully read here. In total, tests for the optimal location of the buttons in AT&T took 16 properties of numbers.
Specialists of the company have examined each of the designs and tested them for speed dialing and the number of errors in phone numbers that occur under specific system. Finally managed to select a group of five options for the location of buttons, had the lowest percentage of “marriage” and allowing users of the phone will dial the number. As it turned out, the optimum for these indicators are from a system with two vertical or horizontal rows of five buttons each, the system host the square buttons 3×3 plus one button from the bottom, and two so-called circular option, which resembled the arrangement of numbers on the phones with a rotary dial.
Then, from the “competition” has been deleted design with two vertical rows of buttons. Despite his formal convenience for users, study participants noted that they do not like the way this version looks externally.
In turn, the engineers AT&T said that the circular layout options are not best suited for use on existing phones. The companys experts were in favor of using square and rectangular property, as they, in their opinion, were better from the design point of view. The final selection consisted of a square array of 3×3 plus one button at the bottom and made of two horizontal stripes of digits.
In the survey, with a margin of 12 votes to 3, defeated, located in two strips of five buttons each. However, later as the main was chosen the other option, which was the final standard.
What exactly was guided in AT&T when making this decision, it is not known. According to some, the decision was made concrete by the engineer of the company, which could take into account their own aesthetic preferences or features of those phones on which he was to introduce a new system of buttons. Anyway, in the end, the location of the 3×3 plus one engraft and still, with the addition of slots for * and # applies to both landline phones and mobile devices, where the physical buttons have been replaced by touch.