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1991-12-31
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Recommendation T.351
IMAGING PROCESS OF CHARACTER INFORMATION
ON FACSIMILE APPARATUS
(Melbourne, 1988)
0 Introduction
This Recommendation defines the page formatting characteristics of the
information conversion process, for imaging character-information on a facsimile
apparatus.
1 Scope and field of application
This Recommendation intends to specify the method for positioning in a
correct manner character structured messages, in facsimile pages, conforming to
the format defined in Recommendation T.4 Group 3 facsimile apparatus, and
Recommendation T.563 for facsimile Group 4 apparatus. The intention is to insure
the printing of the information inside the guaranteed printable area of the
facsimile pages.
This Recommendation specify in terms of facsimile picture elements (pels),
the initial position and spacing of the characters along the lines and the
spacing between the lines, for creating a facsimile page from the character
structured information. It does not define neither the shape, nor the repertoire
of the characters to be imaged, which is of the responsibility of the
application.
Different types of character encoded information, to be printed on both
Group 3 and Group 4 facsimile apparatus, are considered, namely teletex, telex,
videotex and IA 5 text.
Consideration of mixed mode information requires further study.
This Recommendation applies when interworking implying image conversion
between different type of information, including facsimile, is required within a
regulated service, such as MHS service.
2 References
- Recommendation F.1: Operational provisions for the international public
telegram service.
- Recommendation S.5: Standardization of page-printing start-stop
equipment and cooperation between page-printing and tape-printing
start-stop equipment (ITA No. 2).
- Recommendation T.4: Standardization of Group 3 facsimile apparatus for
document transmission.
- Recommendation T.50: International Alphabet No. 5.
- Recommendation T.60: Terminal equipment for use in the Teletex service.
- Recommendation T.61: Character repertoire and coded character sets for
the international Teletex service.
- Recommendation T.563: General aspects of Group 4 facsimile apparatus.
- Recommendation X.408: Message handling systems: Encoded information
type conversion rules.
3 Definitions
See the Recommendations quoted in reference.
4 Basic principles
The figures given in this Recommendation, in terms of number of picture
elements and facsimile lines, refer to the standard values defined for the
resolution in Recommendation T.4 for Group 3 facsimile apparatus (1728 pels/215
mm and 3.85 lines/mm), and in Recommendation T.563 for Group 4 facsimile
apparatus (1728 pels/219.46 mm and 200 lines/25.4 mm).
These figures are defined relatively to the transmitted facsimile lines.
The reference position of the first character line is defined using the
base line and home position concepts, as defined in Recommendation T.60, Annexes
A and B.
5 Imaging of Teletex messages
The figures of this Recommendation are derived from the figures given in
Recommendation T.60 for the basic printable area of Teletex, with the same
capability of printing a defined number of characters in the left margin,
relatively to the home position.
The Teletex pages, to be imaged on facsimile equipments, conform to the
character repertoire and character sets defined in Recommendation T.61 and to the
pages formats defined for the basic printable area in Recommendation T.60.
5.1 Reference position
Table 1/T.351 defines the position of the 5th base line and of the home
Fascicle VII.5 - Rec. T.351 PAGE1
position, relatively to which is referred the first line of written text,
according to Recommendation T.60.
Both horizontal and vertical orientations of the paper are considered. For
the horizontal orientation, it is assumed that the printing on the facsimile
equipment is performed, starting from the left side of the written text.
TABLE 1/T.351
Reference position for printing Teletex pages
Home position 5th base line
Horizontal Vertical Horizontal Vertical
orientation orientation orientation orientation
(fax line) (pel) (pel) (fax line)
Fax G3 79th 205th 1474th 82th
Fax G4 148th 205th 1474th 164th
5.2 Character spacing
t
to a character spacing value. Table 2/T.351 defines the values to be used for
imaging the characters along the lines, depending on the possible value of the
spacing defined for the Teletex page format.
PAGE2 Fascicle VII.5 - Rec. T.351
TABLE 2/T.351
Values of character spacings
Character spacing value
Defined for Horizontal Vertical
Teletex orientation orientation
(mm) (fax line) (pels)
Fax G3 2.54 10 20
2.12 8 16
1.69 7 14
Fax G4 2.54 20 20
2.12 16 16
1.69 14 14
5.3 Line spacing
The position of the first character line in the facsimile page is defined
from the figures of Table 1/T.351; the following character line are positioned
according to a line spacing value. Table 3/T.351 defines the values to be used
for imaging the characters lines on the facsimile page, depending on the line
spacing value defined for the Teletex page format.
TABLE 3/T.351
Values of line spacing
Line spacing value
Defined for Horizontal Vertical
Teletex (mm) orientation orientation (fax
(pels) lines)
Fax G3 4.23 32 16
6.35 48 24
8.47 64 32
3.175 24 12
5 38 19
Fax G4 4.23 32 32
6.35 48 48
8.47 64 64
3.175 24 24
5 38 38
5.4 Superscript/subscript
In the Teletex message, the superscript and subscript functionalities,
Fascicle VII.5 - Rec. T.351 PAGE1
result in an offset in the printing position of the concerned characters. The
allowed offset value for imaging the Teletex pages on the facsimile page is
defined in Table 4/T.351.
PAGE2 Fascicle VII.5 - Rec. T.351
TABLE 4/T.351
Offset values for supercript/subscript
Offset value
Defined for Horizontal Vertical
Teletex orientation orientation
(mm) (pels) (fax lines)
Fax G3 2.12 16 8
Fax G4 2.12 16 16
6 Imaging of Telex messages
The telex messages conform to the character set defined in Recommendation
F.1, and to the format defined in Recommendation S.5.
When imaged on a facsimile equipment, the telex messages are divided in
pages of 55 text lines, as a maximum.
Only the vertical orientation of the paper is to be considered.
The first character of each text line in a page is positioned according to
the home position defined in Table 1/T.351.
The first line is referred to the 5th base line, as defined in Table
1/T.351.
The character spacing values to be used are those defined in Table 2/T.351
for the 2.54 mm spacing.
The line spacing values to be used are those defined in Table 3/T.351 for
the 4.23 mm spacing.
7 Imaging of videotex messages
For further study.
8 Imaging of IA 5 text messages
IA 5 messages conform to the character set defined in Recommendation T.50.
When imaged on a facsimile equipments, IA 5 messages are formatted in
pages of 55 lines of 80 characters.
Only the vertical orientation of the paper is to be considered.
The first character of each text line in a page is positioned according to
the home position defined in Table 1/T.351.
The first line is referred to the 5th base line, as defined in Table
1/T.351.
The character spacing values to be used are those defined in Table 2/T.351
for the 2.12 mm spacing.
The line spacing values to be used are those defined in Table 3/T.351 for
the 4.23 mm spacing.
Fascicle VII.5 - Rec. T.351 PAGE1