FOREWORD
The International Telecommunication Union (ITU) is the United Nations
specialized agency in the field of tele¡©com¡©mu¡©ni¡©ca¡©tions. The ITU
Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU.
ITU-T is responsible for studying technical, operating and tariff questions and
issuing Recommendations on them with a view to standardizing telecommunications
on a worldwide basis.
The World Telecommunication Standardization Assembly
(WTSA), which meets every four years, establishes the topics for study by the
ITU‑T study groups which, in turn, produce Recommendations on these topics.
The approval of ITU-T
Recommendations is covered by the procedure laid down in WTSA Resolution 1.
In some areas of information technology which fall within ITU-T's
purview, the necessary standards are prepared on a collaborative basis with ISO
and IEC.
NOTE
In this Recommendation, the expression
"Administration" is used for conciseness to indicate both a
telecommunication administration and a recognized operating agency.
ITU draws attention to the possibility that the
practice or implementation of this Recommendation may involve the use of a
claimed Intellectual Property Right. ITU takes no position concerning the
evidence, validity or applicability of claimed Intellectual Property Rights,
whether asserted by ITU members or others outside of the Recommendation
development process.
As of the date of approval
of this Recommendation, ITU had not received notice of intellectual property,
protected by patents, which may be required to implement this Recommendation.
However, implementors are cautioned that this may not represent the latest
information and are therefore strongly urged to consult the TSB patent database.
ã ITU 2001
All rights reserved. No part of this publication may be reproduced or
utilized in any form or by any means, electronic or mechanical, including
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CONTENTS
Page
1 Use of digits and letters on telephone sets...................................................................... 1
2 Rotary dials.................................................................................................................. 1
3 Push-buttons or keys.................................................................................................... 2
3.1 Ten push-buttons.......................................................................................................... 2
3.1.1 Arrangement and numbering............................................................................. 2
3.1.2 Symbols.......................................................................................................... 3
3.2 12 push-buttons............................................................................................................ 3
3.2.1 Arrangement.................................................................................................... 3
3.2.2 Symbols.......................................................................................................... 3
3.3 Dual mode and engraving.............................................................................................. 4
3.4 Design of symbols......................................................................................................... 4
3.5 Position of figures, letters and symbols on
push-button sets............................................ 4
3.6 Tactile identifier on the "5" button.................................................................................. 5
4 Additional push-buttons for use on telephones............................................................... 5
4.1 General......................................................................................................................... 5
4.2 Specific recommendations............................................................................................. 6
4.2.1 Register recall push-button............................................................................... 6
ITU-T Recommendation E.161
Arrangement of digits, letters and symbols
on telephones and other devices that can be used for gaining access to a
telephone network
1.1 For
the automatic international service, it is preferable that the national
numbering plan should not involve the routine use of letters, e.g. to designate
local exchanges (associated with digits). However, letters may be used to
designate the names of particular services, facilities, organizations or
individual subscribers. The allocation of such mnemonics (and their equivalent
national numbers) is a national matter.
1.2 For
countries using letters in telephone numbers, it would be helpful to include in
the directory a table for converting the letter codes into digits (see 2.2).
1.3 It
would also be desirable to request those subscribers assigned mnemonic codes
(particularly if they have considerable international traffic) to show on their
letterheads, below their national telephone number, the international number
with digits only. (See ITU-T E.123.)
2.1 For
countries which have not yet adopted any specific type of dial, the digits on
the dial should be arranged in the following order: 1, 2, 3, ... , 0 as shown
in Figure 1.
Figure 1/E.161 – Rotary dial
2.2 Where
letters as well as digits appear on a dial or its surround, the recommended
relationships between the letters and the digits are as shown below:
|
|
|
1
|
2 ABC
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3 DEF
|
|
4 GHI
|
5 JKL
|
6 MNO
|
|
7 PQRS
|
8 TUV
|
9 WXYZ
|
|
|
0
|
|
The standard arrangement and numbering for
push-buttons corresponding to the digits 1 to 0 is as shown below:
1 2 3
4 5 6
7 8 9
0
Extensive research has shown that this
arrangement leads to shorter entry times and lower error rates than other
arrangements.
Where a need exists within an
Administration for a 2 ¡¿ 5 array or a 5 ¡¿ 2 array for use on special telephone
apparatus, the arrays should be as shown below:
1 2
1 2 3 4 5 3 4
6 7 8 9 0 5 6
7 8
9 0
NOTE – User dialling performance on these
special arrays is slightly inferior to that on the standard array given above.
While numbering plans using only digits are
widely used, there are advantages in allowing the use within these numbering
plans of alphabetic equivalents for frequently used numbers (see 1.1). The use
of letters rather than numbers is also convenient for data entry (interactive
applications, entry of passwords, etc.) after a call has been established.
The recommended relationships between the letters and the digits are the same
as shown in 2.2,
including its footnote. Care must be taken when letters and a digit are
associated with a key such that legibility of the digit is not impaired.
The preferred and recommended arrangement
for the keys of a separate numeric keypad on a multi-functional terminal used
both for the entry of telephone number information and data is the standard
arrangement shown at the beginning of this clause.
Exceptionally, for devices intended to be
used principally for data entry but which may sometimes be used to enter
telephone number information, the arrangement whereby the first and the third
row of the standard ITU-T arrangement are interchanged may be used.
Also exceptionally, telephone number
information may be input from the row of numeric keys.
1 2 3 4 5 6 7 8 9 0
of an alpha-numeric keyboard.
The symbols for these buttons are the
digits 1 to 0 as indicated in the arrangement of 3.1.1. These buttons are to be
known as button 1, button 2, etc.
For 12 push-buttons the standard
arrangement shown in 3.1.1 is extended by two additional buttons, one to the
left and the other to the right of the button 0, thus making a pattern of
four horizontal rows of three buttons each forming a 4 ¡¿ 3 array.
Two buttons may also be added to the 5 ¡¿ 2
array shown in 3.1.1. These should be located below and in line with
buttons 9 and 0, thus making a 6 ¡¿ 2 array.
On the 4 ¡¿ 3 array, the symbol on the
button which is immediately to the left of the button 0 (on the 6 ¡¿ 2 array,
the corresponding button is located below 9, and on the 2 ¡¿ 6
array to the right of button 5) and which, according to UIT-T Q.23, is
used to transmit the frequency pair 941 Hz and 1209 Hz, should have a
shape easily identified as the general shape shown in Figure 2.
Figure 2/E.161
The symbol will be known as the star or the equivalent term in other
languages.
On the 4 ¡¿ 3 array, the symbol on the
button which is immediately to the right of the button 0 (in the 6 ¡¿ 2 array,
the corresponding button is located below the button 0) and which,
according to UIT‑T Q.23, is used to transmit the frequency pair
941 Hz and 1477 Hz, should conform in shape to the specifications
given in Figure 3 or 4. This symbol shall consist of four lines of
equal length (b) forming two pairs of parallel lines. One pair is
horizontal while the other is vertical or inclined to the right at an
angle ¥á of 80o as shown in Figure 4. It will be seen that two pairs of
parallel lines overlap. The ratio a/b where a
is the overlap, shall be between 0.08 and 0.18.
Figure 3/E.161
Figure 4/E.161
The preferred values are either:
– ¥á
= 90o with a/b = 0.08;
– ¥á
= 80o with a/b close to the upper limit of 0.18.
The symbol may be referred to as the square
or the most commonly used equivalent term in other languages.
The additional buttons with these symbols
will be placed as shown below:
|
Standard 4 ¡¿ 3 array
|
6 ¡¿ 2 array
|
2 ¡¿ 6 array
|
|
1 2 3
|
1 2
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1
2 3 4 5 
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|
4
5 6
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3 4
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6
7 8 9 0 #
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|
7
8 9
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5 6
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|
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0 #
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7 8
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|
|
|
9 0
|
|
|
|
#
|
|
Dual mode and engraving of the buttons and # are acceptable on telephones and on
multi-functional terminals.
Symbol size and the line thickness should
be appropriate to provide optimal recognition.
The figures, letters and symbols used for
dialling should be unambiguously associated with the corresponding buttons,
preferably, if adequate space is available, by being on the faces of the
buttons themselves.
To assist blind and visually impaired
people in identifying the dialling push-buttons and otherwise to facilitate
dialling under low light conditions, it is recommended that the button with the
"5" be marked with a tactile identifier so that the button can be
identified by the sense of touch.
The preferred locations of the tactile
identifier are:
– In
the middle of the "5" button.
– As
near the middle of the "5" button as possible.
– On
the surface of the "5" button that is pressed when it is activated.
It is recommended that the tactile
identifier is positioned in such a way that it will not obscure the legibility
of the marking on the "5" button (see Figure 5).
Figure 5/E.161
If none of these locations can be used,
e.g. on small keys, alternative positions of the tactile identifier are
acceptable. However, the tactile identifier shall unambiguously identify the
"5" button.
The preferred form of the tactile
identifier on the "5" button is a distinct raised round dot (see
Figure 6).
The recommended dimensions of the raised
round dot are:
– Height
0.6 mm (+0.2 mm).
– Diameter
1.5 mm (+0.2 mm).
Figure 6/E.161
For purposes other than dialling, additional
push-buttons may be required on a telephone. For example, a telephone may have
a push-button to recall during an active call, control logic (e.g. a
register) or an operator, or to effect the transfer of an active call to
another station. To prevent
subscriber confusion it may be desirable that the symbols used on those
push-buttons which have identical functions be standardized.
For the recall of a register during an
active call, the following methods are possible:
– a
switchhook flash;
– a
depression of one of the push-buttons of the normal 10 or 12 button array;
– a
depression of another push-button specially provided for this purpose –
the register recall push-button.
From the human factors viewpoint the
depression of a push-button for register recall seems to be preferable to the
use of a switchhook flash.
If a special register recall push-button is
used, this push-button should be designated with the symbol R (capital)
on, or next to the push-button. The push-button should be clearly
distinguishable and spatially separated from the standard 12-push-button array.
This symbol is recommended because:
a) it
symbolizes the term "Recall" in a number of languages;
b) studies
have shown that it is subject to minimal auditory and visual confusion;
c) it
avoids the difficulties inherent in specific technical terms for any lay
subscribers.
The exact position, shape and colour of the
button should not be standardized at the present time. Such standardization
would inhibit design innovation and be unnecessarily restrictive.
References
[1] The layout of digits on push-button
telephones – a review of the literature. TELE, No. 1, 1982 (copies available at the Library of the Telia,
S-12386 FARSTA).
[2] ETSI
ES 201 381 V1.1.1 (1998), Human Factors (HF); Telecommunications keypads and
keyboards; Tactile identifiers.
