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THE TOUCH-TONE® "DIAL"
The TOUCH-TONE® telephone made its
Bell System commercial debut in November, 1963 and is well on
its way to success. Customer enthusiasm for the new pushbutton
service can be seen in some typical comments:
"The whole thing is like
magic. You can dial very fast and it’s just wonderful."
"Speed, simplicity...the sound
is delightful."
"Quite inexpensive for the
convenience you get -- Why, I hardly notice the difference in
the bill each month."
"It cuts dialing time in half,
and to a businessman like myself, this means saving
money."
Along with
customer interest in TOUCH-TONE® service, there has been some
natural curiosity about the new telephone. Why does it look
the way it does? How did Bell Labs go about picking this
particular arrangement of buttons instead of some other? When
the development of the TOUCH-TONE® telephone began, Bell Labs
human factors engineers realized that the arrangement of the
buttons had to be considered very carefully. The success or
failure of this giant step in communications would depend in
large part on how our customers felt using the new telephone.
Consequently, a great deal of attention was given to the
button array that was to be used and to such other
characteristics of the buttons as their size, and shape, the
distance between them, how much force must be used to operate
them. Studies participated in by Bell Labs as far back
as 1955 indicated that most people expect to find letters of a
pushbutton set arranged left-to-right order in horizontal
rows, starting with the top row -- the order in which we read,
in fact. As a test of pushbutton arrangements in a form
closer to the intended use, telephones were made using 16
different arrays -- rows, circles, triangles, crosses, even
one very like the layout of the rotary dial. Volunteer
participants spent weeks testing the different layouts to
determine the speed, error rate, and preference index of each
one. Final choice for the TOUCH-TONE® telephone was an array
of three rows of three buttons each, with the letters and
numbers arranged in a left-to-right, top-to-bottom order, and
the "Zero-Operator" button centered on a fourth row.
Once the arrangement was decided upon, other tests were made
to determine the best size and spacing for the buttons. If
they were too close together, one button would be difficult to
push without depressing others at the same time. If they were
too large, the entire group of buttons couldn’t be easily
taken in at a glance, and more important, they couldn’t fit
on the telephone set. Even the pushbutton action, or
"feel" came in for study. Human-factors tests showed
that most people preferred a smooth button action -- rather
than a "snap" -- with a definite, but slightly
cushioned, stop. The first design concept incorporating the
results of laboratory tests was translated into plastic and
metal in the Model Shop at Western Electric’s Indianapolis Works. Then began a
new phase of the Bell System pattern of matching a new design
to the customer. The preliminary TOUCH-TONE® models were
installed temporarily in four cities. In all, some 500
homes and offices became laboratories-in-miniature. The
telephone sets used were still considered experimental. While
testing under field conditions was going on, more human
factors experiments back at Bell Labs continued the search for
the best possible combination of pushbutton characteristics.
As the engineers moved closer to their goal, they checked each
step of progress against interviews with people using
TOUCH-TONE® telephones in their homes and places of business.
By the time the field trials were over and the decision had
been made to market test TOUCH-TONE® service before offering
it to the general public, a number of design changes had been
made. Button size had been cut 65 per cent. The letter
"I" and numeral "1", next to each other
vertically, were made more distinct in appearance. The force
required to depress the buttons was doubled to overcome
accidental pushing of more than one button at the same time.
In line with the modern concept of TOUCH-TONE® calling, the
telephone was redesigned, the round dial face given a clean,
square look. The buttons themselves, white with black letters
in the test models, were made gray with white letters. The
surface of the buttons was hollowed gently to fit the
fingertips. The results of the marketing trial proved every
effort to have been worthwhile. Ninety-six per cent of the
buyers said they thought TOUCH-TONE® service was an
improvement. Since its release to Bell System customers on a
gradual basis, the TOUCHTONE® telephone has been meeting with
gratifying success, proving the worth of customer-tested
products.
Source:
Bell Telephone Laboratories, March 1964
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