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InfoMagic Standards 1994 January
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InfoMagic Standards - January 1994.iso
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.rs
.\" Troff code generated by TPS Convert from ITU Original Files
.\" Not Copyright ( c) 1991
.\"
.\" Assumes tbl, eqn, MS macros, and lots of luck.
.TA 1c 2c 3c 4c 5c 6c 7c 8c
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.EN
.nr LL 40.5P
.nr ll 40.5P
.nr HM 3P
.nr FM 6P
.nr PO 4P
.nr PD 9p
.po 4P
.rs
\v | 5i'
.sp 2P
.LP
\fBRecommendation\ T.100\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBINTERNATIONAL\ \fR \fBINFORMATION\ EXCHANGE\ FOR\ INTERACTIVE\ VIDEOTEX\fR
.EF '% Fascicle\ VII.5\ \(em\ Rec.\ T.100''
.OF '''Fascicle\ VII.5\ \(em\ Rec.\ T.100 %'
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1980; amended at Malaga\(hyTorremolinos, 1984)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.ce 1000
CONTENTS
.ce 0
.sp 1P
.LP
Preamble
.sp 1P
.RT
.LP
\ 1
Purpose and scope of this Recommendation
.LP
\ 2
General Videotex coding structure
.LP
\ 3
Common features
.LP
\ 4
Representation of alphanumeric characters in
a Videotex system
.LP
\ 5
Alphamosaic option
.LP
\ 6
Alphageometric option
.LP
\ 7
Dynamically redefinable character sets (DRCS) option
.LP
\ 8
Alphaphotographic option
.LP
\ 9
Service enhancements
.LP
10
Line and end\(hyto\(hyend protocols
.LP
11
Interworking with other services
.sp 1P
.LP
\fIAnnex\ A\fR \ \(em\ The extension scheme of ISO 2022
.sp 9p
.RT
.LP
\fIAnnex\ B\fR \ \(em\ Repertoire of graphic characters
.LP
\fBPreamble\fR
.sp 1P
.RT
.sp 2P
.LP
The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR
.sp 9p
.RT
.PP
(a)
that there is increasing interest in public
network\(hybased new interactive information retrieval services using domestic
television receivers suitably supplemented, or other apparatus, as terminal
equipment;
.PP
(b)
that the CCIR is studying standards for broadcast
\fITeletext\fR services for general reception and has expressed a view
that it is desirable that terminal equipment compatibility should exist
between broadcast Teletext systems for general reception and public network\(hybased
data bank
systems;
.PP
(c)
that such services should be provided over public
networks in accordance with CCITT Recommendations and may be required to
operate as an international service;
.PP
(d)
that such services may interwork with terminals provided for text communication
services (Teletex for example);
.PP
(e)
that some Administrations intend to have an early
introduction of, or have already introduced,
public interactive \fIVideotex\fR services
;
.sp 1P
.LP
\fIunanimously recommends\fR
.sp 9p
.RT
.PP
that the following technical provisions be applied for
international information exchange for
interactive Videotex
service.
.bp
.sp 2P
.LP
\fB1\fR \fBPurpose and scope of the Recommendation\fR
.sp 1P
.RT
.sp 1P
.LP
1.1
\fIPurpose\fR
.sp 9p
.RT
.PP
1.1.1
The purpose of this Recommendation is:
.sp 9p
.RT
.LP
a)
to facilitate an orderly introduction of early
Videotex services
(including the continuation of existing services, with a
clear identification of potential enhancements) that need to
be considered in future developments;
.LP
b)
to identify parameters needed to design
Videotex
terminals
; and
.LP
c)
to provide technical recommendations desirable for potential interworking
of other services with Videotex services.
.sp 2P
.LP
1.2
\fIScope\fR
.sp 1P
.RT
.PP
1.2.1
This Recommendation describes the characteristics of coded
information that is exchanged between countries participating in the
international interactive Videotex service (as described in
Recommendation\ F.300) and defines the display features corresponding to its
various elements.
.sp 9p
.RT
.PP
1.2.2
Videotex systems are text communication systems having in
addition the capability of a given level of pictorial representation and a
repertoire of display attributes. The text and the pictures obtained are
intended to be displayed using the current television\ (TV) raster standards
of the different countries.
.PP
1.2.3
Different options are offered as a choice for the Administrations to implement
their national services. Substantial degrees of
compatibility exist between these options, but some transcoding may be
necessary to facilitate interworking.
.PP
1.2.4
For the international service, four different options for
representing pictorial information have been recognized:
.LP
a)
mosaic character
sets;
.LP
b)
geometric system;
.LP
c)
dynamically redefinable character sets
;
.LP
d)
photographic representation.
.PP
These options are not mutually exclusive and it is possible that systems
may develop using two or more options.
.PP
1.2.5
For international interworking, two categories of TV systems
have to be considered:
.sp 9p
.RT
.LP
a)
systems having a vertical resolution of 525 lines per TV
frame at 30\ TV frames per second;
.LP
b)
systems having a vertical resolution of 625\ lines per TV
frame at 25\ TV frames per second.
.PP
1.2.6
Interworking problems at the pictorial level between countries having different
recognized pictorial systems and/or television standards
require further study.
.sp 9p
.RT
.PP
1.2.7
This Recommendation is structured as follows:
.sp 9p
.RT
.LP
\(sc\(sc\ 1,\ 2\ and\ 3
deal with the features common to all the
options;
.LP
\(sc\ 4
deals with the coding of characters of the Videotex
alphanumeric repertoire defined in Annex\ B;
.LP
\(sc\ 5
deals with the alphamosaic option;
.LP
\(sc\ 6
deals with the alphageometric option;
.LP
\(sc\ 7
deals with the dynamically redefinable
character sets (DRCS) option;
.LP
\(sc\ 8
deals with the alphaphotographic option;
.LP
\(sc\ 9
deals with future enhancements and identifies
features requiring further study such as: audio,
downloaded software, motion,\ etc.;
.LP
\(sc\ 10
deals with line and end\(hyto\(hyend protocols;
.LP
\(sc\ 11
deals with interworking with other services.
.PP
Some of these parts have not been completed, and therefore contain guidelines
towards future extensions rather than a complete technical
specification.
.bp
.sp 2P
.LP
\fB2\fR \fBGeneral\fR
\fBVideotex coding\fR \fBstructure\fR
.sp 1P
.RT
.sp 1P
.LP
2.1
\fIGeneral\fR
.sp 9p
.RT
.PP
2.1.1
The basis of the coding structure for the Videotex service is Recommendation\
T.50 and the international standards ISO\ 2022, ISO\ 6937
for the 7\(hybit environment. Specifically, the shift\(hyin code SI\ (0/15)
invokes
the G0 set for
alphanumeric text mode
of operation, and the shift\(hyout code SO\ (0/14) invokes the\ G1 set,
for all the models (see Annex\ A). The use of the 8\(hybit coding scheme
is for further study.
.sp 9p
.RT
.PP
2.1.2
In addition to the provisions made by ISO\ 2022, the transmission of alphabetic
characters having diacritical signs is effected by transmitting the code
representing the diacritical mark together with the code of the basic alphabetic
character.
.PP
2.1.3
The different options are designated (and invoked) by specific
escape sequences.
.sp 2P
.LP
2.2
\fIDesignation and invocation in the context of the alphamosaic\fR
\fIoption\fR
.sp 1P
.RT
.PP
2.2.1
Two different modes for the
alphamosaic option
have
been identified. They differ in their display control sets. These control
sets are designated as the\ C1 set by the following control sequences:
ESC\ 2/2\ 4/0 for the serial mode and ESC\ 2/2\ 4/1 for the parallel mode, as
assigned by ISO. Individual controls are represented by:
ESC\ F\de\usequences.
.sp 9p
.RT
.PP
2.2.2
The mosaic graphics set is designated (in the parallel mode) as
the G1 set by an escape sequence ESC\ 2/9\ 6/3 as allocated by\ ISO.
.sp 2P
.LP
2.3
\fIDesignation and invocation in the context of the\fR
\fIalphageometric option\fR
.sp 1P
.RT
.PP
2.3.1
The
alphageometric coding
scheme is to be designated
and invoked by the escape sequence\ ESC\ 2/5\ (5/x) in accordance with
\(sc\ 5.3.8 of ISO\ 2022 standard. This designates and invokes a complete
code with interpretation as follows.
.sp 9p
.RT
.PP
2.3.2
All the meanings and interpretation of Recommendation T.50
and ISO\ 2022 remain the same, including\ C0, G0\ and\ G2 with the exception
of\ SI and\ SO. The codes of the\ G1 set and their meanings and interpretations
are as described in \(sc\ 6.
.PP
2.3.3
The designation and invocation of the complete code by the
sequence ESC\ 2/5\ (5/x) is to be terminated only by ESC\ 2/9\ (F) or ESC\
2/13\ (F), designating a normal\ G1\ set.
.sp 2P
.LP
2.4
\fIDesignation and invocation in the context of DRCS\fR
.sp 1P
.RT
.PP
2.4.1
A DRCS is a set of characters whose shapes are sent from the
service and down\(hyloaded via the line. It may be used to represent alphabetic
characters, special symbols, or picture element symbols for constructing
fine graphics. Once loaded, the\ DRCS are regarded as members of a library
that can be designated by appropriate\ ESC sequences as G0, G1, G2, G3\
sets. One scheme is described in \(sc\ 7 in the context of a general architecture.
.sp 9p
.RT
.sp 1P
.LP
2.5
\fIDesignation and invocation in the context of the alphaphotographic\fR
\fIoption\fR
.sp 9p
.RT
.PP
(For further study.)
.RT
.sp 2P
.LP
\fB3\fR \fBCommon features\fR
.sp 1P
.RT
.sp 1P
.LP
3.1
\fIGeneral\fR
.sp 9p
.RT
.PP
3.1.1
The features pertaining to individual systems will be described in the
corresponding paragraphs. The common features comprise common display
features and common control functions.
.bp
.sp 9p
.RT
.sp 2P
.LP
3.2
\fICommon display features\fR
.sp 1P
.RT
.PP
3.2.1
The \fIdefined\fR
\fIdisplay area\fR is that rectangular
position of the display in which all text and pictorial images may be presented
(see Figure\ 1/T.100).
.sp 9p
.RT
.PP
3.2.2
The
\fIborder area\fR is that part of the visible display of a terminal that
is outside the defined display area (see Figure\ 1/T.100).
.LP
.rs
.sp 10P
.ad r
\fBFigure 1/T.100, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
3.3
\fICommon format effector and\fR
\fIcode extension\fR \fIcontrol\fR
\fIfunctions\fR
.sp 1P
.RT
.sp 1P
.LP
3.3.1
\fIGeneral\fR
.sp 9p
.RT
.PP
3.3.1.1
The format effector control functions described for the
Videotex system permit the active drawing position to be moved on the visible
display area. These are taken from the C0 set (see Figure\ 2/T.100) together
with the \fISpace\fR character\ 2/0. In order to permit interworking between
Videotex and other text communications services, these control functions
have functional compatibility to the extent possible with the basic\ C0
control set utilized by these other services.
.sp 9p
.RT
.sp 2P
.LP
3.3.2
\fIFormat effector controls\fR
.sp 1P
.RT
.PP
3.3.2.1
Some of the format effector control functions may be used from terminal
to computer with different meanings.
.sp 9p
.RT
.sp 1P
.LP
3.3.2.2
\fIActive position backward (APB)\fR
.sp 9p
.RT
.PP
This control function causes the active position to be
moved one character position backwards on the same row. APB on the first
character position on the row moves the active position to the last character
position of the preceding row. APB on the first character position on the
first row moves the active position to the last character position of the
last
row.
.RT
.sp 1P
.LP
3.3.2.3
\fIActive position forward (APF)\fR
.sp 9p
.RT
.PP
This function causes the active position to be moved
to the next character position forward on the same row. At the last position
on the row, this control moves the active position to the first character
position on the following row. APF on the last character position of the
last row moves the active position to the first character position of the
first row.
.RT
.sp 1P
.LP
3.3.2.4
\fIActive position down (APD)\fR
.sp 9p
.RT
.PP
This function causes the active position to be moved
to the equivalent character position on the following row. APD on the last
row moves the active position of the equivalent character position of the
first row of the display frame or causes a roll\(hyup to be made.
.bp
.RT
.LP
.rs
.sp 47P
.ad r
\fBFigure 2/T.100, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.3.2.5
\fIActive position up (APU)\fR
.sp 9p
.RT
.PP
This function causes the active position to be moved
to the equivalent character position on the preceding row. APU on the first
row moves the active position to the equivalent character position on the
last row of the same display frame.
.RT
.sp 1P
.LP
3.3.2.6
\fIClear screen (CS)\fR
.sp 9p
.RT
.PP
This function causes the screen to be cleared and causes the
active position to be moved to the first character position on the first
row.
.RT
.sp 1P
.LP
3.3.2.7
\fIActive position return (APR)\fR
.sp 9p
.RT
.PP
This function causes the active position to be moved to the first character
position of the same row.
.RT
.sp 1P
.LP
3.3.2.8
\fISpace (SP)\fR
.sp 9p
.RT
.PP
A control function that causes the active position to be moved one character
width forward on the same row. It is also regarded as a graphic
character with no foreground. In those systems that define an explicit
background, the space copies the background colour into the active position
and moves the active position one character width forward. If used in conjunction
with the inversion attribute it copies the foreground colour into the active
position and moves the active position one character width forward.
.RT
.sp 1P
.LP
3.3.2.9
\fICancel (CAN)\fR
.sp 9p
.RT
.PP
A control function that fills all the character
positions of the row, after the active position, with spaces and returns the
active position to its original value.
.RT
.sp 2P
.LP
3.3.3
\fICode extension control functions\fR
.sp 1P
.RT
.PP
3.3.3.1
Code extension control functions are used to expand the
capability of the 7\(hybit code beyond 128\ different characters or functions.
Code extension functions alter the meaning of a number of characters following
them.
.sp 9p
.RT
.sp 1P
.LP
3.3.3.2
\fIEscape (ESC)\fR
.sp 9p
.RT
.PP
A control character that is used to provide
additional control functions other than transmission control functions
and that alters the meaning of a limited number of contiguously following
bit
combinations in the manner specified in Recommendation\ T.51.
.RT
.sp 1P
.LP
3.3.3.3
\fIControl sequence introducer (CSI)\fR
.sp 9p
.RT
.PP
A code extension control function that is used to provide coded
representations for additional control functions, in particular for control
functions with parameters such as presentation control functions.
.RT
.sp 1P
.LP
3.3.3.4
\fIShift\(hyout (SO)\fR
.sp 9p
.RT
.PP
A control character that is used in conjunction
with the \fIShift\(hyin\fR character to extend the graphic character set
of the code and that alters the meaning of the bit combinations of columns\
2\(hy7 of the code table, until the occurrence of the \fIshift\(hyin\fR
character, except that the
meaning of the bit combinations corresponding to the \fIspace\fR character
and the \fIdelete\fR character (positions\ 2/0 and\ 7/15) are unaffected.
.RT
.sp 1P
.LP
3.3.3.5
\fIShift\(hyin (SI)\fR
.sp 9p
.RT
.PP
A control character, used in conjunction with the \fIshift\(hyout\fR
character, that reinstates the former meanings of the bit combinations of
columns\ 2\(hy7 of the code table.
.RT
.sp 1P
.LP
3.3.3.6
\fISingle shift (SS2)\fR
.sp 9p
.RT
.PP
This character alters the meaning of the single\(hybit combination
following it. That bit combination must be one of those from columns\ 2\(hy7
except\ 2/0 and\ 7/15. The meaning of the bit combination concerned is derived
from an appropriately designated\ G2 graphic set.
.bp
.RT
.sp 1P
.LP
3.3.3.7
\fISingle shift (SS3)\fR
.sp 9p
.RT
.PP
This character alters the meaning of the single\(hybit combination
following it. That bit combination must be one of those from columns\ 2\(hy7
except\ 2/0 and\ 7/15. The meaning of the bit combination concerned is derived
from an appropriately designated\ G3 graphic set.
.RT
.sp 2P
.LP
3.4
\fIMiscellaneous\fR
.sp 1P
.RT
.sp 1P
.LP
3.4.1
\fINull (NUL)\fR
.sp 9p
.RT
.PP
This function may occur in non\(hytransparent modes in the received
bit stream at the terminal. It shall be regarded as a time filler and
discarded.
.RT
.sp 1P
.LP
3.4.2
\fIEnquiry (ENQ)\fR
.sp 9p
.RT
.PP
A control character used as a request for a response from a remote station,
which response may include station identification and/or station
status.
.RT
.sp 2P
.LP
3.5
\fICoding of control functions\fR
.sp 1P
.RT
.PP
3.5.1
A proposed coding of the control functions described is shown in Figure\
2/T.100 as a\ C0 set, except for CSI which is coded in the C1\ set.
.sp 9p
.RT
.sp 2P
.LP
\fB4\fR \fBRepresentation of \fR \fBalphanumeric characters in a Videotex\fR
\fBsystem\fR
.sp 1P
.RT
.sp 1P
.LP
4.1
\fIGeneral\fR
.sp 9p
.RT
.PP
4.1.1
The repertoire for the Latin alphabet is shown in Annex B. The repertoire
is derived from ISO\ 6937. Terminals capable of displaying a
subset of the Videotex repertoire shall be permitted.
.sp 9p
.RT
.PP
4.1.2
Character repertoires
for non\(hylatin based languages can be accommodated in a similar manner
to the latin alphabet. (For further study.)
.sp 2P
.LP
4.2
\fICoding\fR
.sp 1P
.RT
.PP
4.2.1
Section\ 4.2 describes the coding of characters the shape of
which are stored in the terminal. Some languages require that consecutive
letters or diacritical marks will be joined and that no space appear between
the characters. When an intersymbol space is required, it will be part
of the character description.
.sp 9p
.RT
.PP
4.2.2
The code tables are shown in Figures 3/T.100 and 4/T.100. The
code combinations representing characters not included in the Videotex
repertoire shall not be transmitted.
.PP
4.2.3
All the permitted combinations may be expected in the
international exchange of information between two national services. It
is the responsibility of Administrations to decide whether this exchange
is a direct terminal to data\(hybase operation or has to be performed through
a gateway. See Recommendation\ F.300.
.PP
4.2.4
The graphic characters from columns\ 2, 3, 5, 6 and 7 of the
supplementary set are invoked one at a time by SS2.
.PP
4.2.5
A character with a diacritical mark is transmitted by the
sequence\ SS2, a character from column\ 4 from the supplementary set, and the
appropriate character from the primary set. The diacritical marks are
non\(hyspacing.
.PP
4.2.6
The ISO registration of graphics character sets will indicate any special
features such as their use in conjunction with other graphic character
sets or non\(hyspacing characters, etc.
.PP
4.2.7
For languages based on other than the Latin alphabet further
study is required.
.sp 2P
.LP
\fB5\fR \fBAlphamosaic option\fR
.sp 1P
.RT
.sp 1P
.LP
5.1
\fIGeneral\fR
.sp 9p
.RT
.PP
5.1.1
In the alphamosaic option, the display frame is composed of
defined character positions which may be occupied by any of the characters
of the repertoire. The repertoire is composed of the alphanumeric repertoire
and a mosaic repertoire. The mosaic repertoire is formed by dividing the
character
space into a matrix of 2\ \(mu\ 3\ elements. There are\ 63 different combinations
of these elements.
.bp
.sp 9p
.RT
.LP
.rs
.sp 47P
.ad r
\fBFigure 3/T.100, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 4/T.100, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.PP
5.1.2
Two modes have been identified, which are known as \fIserial\fR and
\fIparallel\fR modes respectively. The two modes are distinguished by their
display control sets which are coded in C1 sets, designated and represented
by
ESC\ F\de\usequences as described in \(sc\ 2.2.1.
.PP
5.1.3
The two modes have common features and specific features
described in \(sc\(sc\ 5.2 to\ 5.4 below.
.LP
5.2
\fICommon \fR \fIcontrol functions\fR
.sp 1P
.RT
.sp 2P
.LP
5.2.1
\fIGeneral functions\fR
.sp 1P
.RT
.sp 1P
.LP
The \fIactive position home (APH)\fR
.sp 9p
.RT
.PP
This function causes the active position to be moved
to the first position of the first row. Its coded representation is\ 1/14 in
Figure\ 2/T.100.
.RT
.sp 1P
.LP
5.2.2
\fIDevice control functions\fR
.sp 9p
.RT
.PP
The following device control functions have been defined.
.RT
.sp 2P
.LP
5.2.2.1
\fIDefinitions\fR
.sp 1P
.RT
.sp 1P
.LP
\fBcursor on (CON)\fR
.sp 9p
.RT
.LP
\fIF:\ curseur en marche (CON)\fR
.LP
\fIS:\ cursor activo (CON)\fR
.PP
The cursor on (CON) causes the active position to be visualized as a marker.
.RT
.sp 1P
.LP
\fBcursor off (COF)\fR
.sp 9p
.RT
.LP
\fIF:\ curseur arr\* | t\*'e (COF)\fR
.LP
\fIS:\ cursor inactivo (COF)\fR
.PP
The cursor off (COF) causes the
active position to be displayed in the same way as other character
positions.
.RT
.sp 1P
.LP
\fBdevice stop (DSP)\fR
.sp 9p
.RT
.LP
\fIF:\ arr\* | t dispositif (DSP)\fR
.LP
\fIS:\ detenci\*'on de dispositivo (DSP)\fR
.PP
The device stop (DSP) causes a designated terminal device to
stop.
.RT
.sp 1P
.LP
\fBdevice start (DST)\fR
.sp 9p
.RT
.LP
\fIF:\ mise en marche dispositif (DST)\fR
.LP
\fIS:\ arranque de dispositivo (DST)\fR
.PP
The device start (DST) causes a designated terminal device to
start.
.RT
.sp 1P
.LP
\fBdevice wait (DW)\fR
.sp 9p
.RT
.LP
\fIF:\ dispositif en attente (DW)\fR
.LP
\fIS:\ espera de dispositivo (DW)\fR
.PP
The device wait (DW) causes a designated terminal device to
pause.
.RT
.sp 1P
.LP
5.2.2.2
\fICoding\fR
.sp 9p
.RT
.PP
CON is coded 1/1, COF is coded 1/4 in the C0 set. DSP, DST
and\ DW functions are coded as 3\(hycharacter sequences of the Form ESC\
3/x\ (P),
where\ x\ =\ 7, 6 and\ 5 respectively, and\ P is a parameter that designates a
particular device.
.bp
.RT
.sp 2P
.LP
5.3
\fISerial mode\fR
.sp 1P
.RT
.sp 1P
.LP
5.3.1
\fIGeneral\fR
.sp 9p
.RT
.PP
5.3.1.1
The serial mode is based on the assumption that changes in
character attributes normally occur in interword spacings. This results in
control characters being serially stored in the page memory and normally
results in their display on the screen as a rectangle in the prevailing
background colour.
.sp 9p
.RT
.PP
5.3.1.2
The C1 set for the serial mode is given in Figure\ 5/T.100. Display controls
of the serial set causes the active position to be moved one character
position forward. In that case, the position thus vacated is to be generally
displayed as a space. The display control \fIhold mosaics\fR ESC\ 5/14
may modify
this situation.
.sp 2P
.LP
5.3.2
\fIDisplay control functions\fR
.sp 1P
.RT
.PP
5.3.2.1
The (F\de\u) codes are listed as follows:
\v'3p'
.sp 9p
.RT
.LP
5.3.2.2
Alpha\ red
\(rt
.LP
Alpha\ green
|
.LP
Alpha\ yellow
|
.LP
Alpha\ blue
\(rk
.LP
Alpha\ magenta
|
.LP
Alpha\ cyan
|
.LP
Alpha\ white
\(rb
.LP
\-v'4P'
\-v'2p'
Controls functions that cause
the currently designated
and invoked alphanumeric
set to be displayed in the
indicated colour until the
occurrence of an explicit colour
control or the end of a row.
\v'1P'
\v'8p'
.sp 1P
.LP
5.3.2.3
\fIFlashing\fR
.sp 9p
.RT
.PP
A control function that causes the characters following it in the
same row to be displayed alternately as they would normally be displayed,
and as spaces, in the prevailing background colour, under the control of
a timing device in the receiver.
.RT
.sp 1P
.LP
5.3.2.4
\fISteady\fR
.sp 9p
.RT
.PP
A control
function that causes the action of \fIflashing\fR to be stopped.
.RT
.sp 1P
.LP
5.3.2.5
\fIStart box\fR
.sp 9p
.RT
.PP
Reserved for starting the action of defining a picture area in a
page of text. (For further study.)
.RT
.sp 1P
.LP
5.3.2.6
\fIEnd box\fR
.sp 9p
.RT
.PP
Reserved for terminating the action of boxing. (For further
study.)
.RT
.sp 1P
.LP
5.3.2.7
\fINormal height\fR
.sp 9p
.RT
.PP
A control function that causes
the graphic characters following it to occupy one character position each.
.RT
.sp 1P
.LP
5.3.2.8
\fIDouble height\fR
.sp 9p
.RT
.PP
A control function that causes the characters following it to
occupy each its active positive and the corresponding position on the following
row.
\v'5p'
.RT
.LP
5.3.2.9
Mosaics\ red
\(rt
.LP
Mosaics\ green
|
.LP
Mosaics\ yellow
|
.LP
Mosaics\ blue
\(rk
.LP
Mosaics\ magenta
|
.LP
Mosaics\ cyan
|
.LP
Mosaics\ white
\(rb
.LP
\-v'5P'
Control functions that cause the mosaic graphic set to be displayed in
the indicated
colour until the occurrence of an explicit
colour control or the end of the row. Unallocated
code table positions (4/0\(hy5/15) cause the
characters of the currently designated and invoked
alphanumeric set to be displayed. This is defined
as \fIblast\(hythrough\fR operation.
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 5/T.100, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
5.3.2.10
\fIConceal display\fR
.sp 9p
.RT
.PP
A control function that causes all characters following it,
although stored in the receiver, to be displayed as spaces until the user
chooses to reveal them.
.RT
.sp 1P
.LP
5.3.2.11
\fIContiguous mosaics\fR
.sp 9p
.RT
.PP
A control function that causes the mosaic set to be displayed as
represented in Figure\ 6/T.100 with all cells being contiguous.
.RT
.sp 1P
.LP
5.3.2.12
\fISeparated mosaics\fR
.sp 9p
.RT
.PP
A control function that causes the mosaics set
to be displayed as represented in Figure\ 6/T.100 with all cells being
separated by the prevailing background colour.
.RT
.sp 1P
.LP
5.3.2.13
\fIBlack background\fR
.sp 9p
.RT
.PP
A control function that causes the background colour to be
black.
.RT
.sp 1P
.LP
5.3.2.14
\fINew background\fR
.sp 9p
.RT
.PP
A control function that causes the current colour
as defined by previous colour control functions to become the new background
colour. The foreground colour is unchanged.
.RT
.sp 1P
.LP
5.3.2.15
\fIHold mosaics\fR
.sp 9p
.RT
.PP
A control function that causes the character positions occupied by display
controls to be displayed by repetition of the last displayable mosaic character.
.RT
.sp 1P
.LP
5.3.2.16
\fIRelease mosaics\fR
.sp 9p
.RT
.PP
A control function that causes the action of \fIhold mosaics\fR to be stopped.
.RT
.sp 2P
.LP
5.3.3
\fIMosaic graphics\fR
.sp 1P
.RT
.PP
5.3.3.1
The \fIserial mosaic\fR graphic set is given in Figure 6/T.100 and the
default conditions of the mode are shown in Table\ 1/T.100.
.sp 9p
.RT
.sp 2P
.LP
5.4
\fIParallel mode\fR
.sp 1P
.RT
.sp 1P
.LP
5.4.1
\fIGeneral\fR
.sp 9p
.RT
.PP
5.4.1.1
The \fIparallel\fR mode is based on an explicit description of the display
frame. This means that the active position is moved only by action of the
format effectors or at the reception of spacing display characters. All
other functions, including display functions, are non\(hyspacing, not depending
on whether or not the terminal needs a space on the screen to process them.
It is the responsibility of the information provider to limit the display
of
pages to pages to fit the capability assumed to receive, without any
modification, pages designed for lower grade terminals.
.sp 9p
.RT
.PP
5.4.1.2
In addition to functions described in \(sc\ 3.3, the
following functions are defined.
.sp 9p
.RT
.sp 1P
.LP
\fBactive position addressing (APA, coded 1/15)\fR
.sp 9p
.RT
.LP
\fIF:\ adressage de position active (APA)\fR
.LP
\fIS:\ direccionamiento de posici\*'on activa (APA)\fR
.PP
This code is followed by two characters. If
these both range from\ 3/0 to\ 3/9, they represent in decimal form respectively
the tens and units of the row address of the first character to be displayed.
This first character will be displayed on the first character position
of the addressed row. If they both range from\ 4/0 to\ 7/14, they represent
respectively the row address and the column address, in binary form with\
6 useful bits, of the first characters to be displayed.
.bp
.RT
.LP
.rs
.sp 47P
.ad r
\fBFigure 6/T.100, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T1.100]\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(276p) .
TABLE\ 1/T.100
.T&
cw(276p) .
{
\fBDisplay modes and control characters\(hyserial mode\fR
}
.TE
.TS
center box ;
cw(54p) | cw(36p) | cw(48p) | cw(54p) | cw(36p) | cw(48p) .
Display mode Set at Set after (see Note) Complementary display mode Set at Set after (see Note)
_
.T&
cw(54p) | cw(36p) | cw(48p) | cw(54p) | cw(36p) | cw(48p) .
Alphanumerics Row start {
\fB4/4\fR
\ 4/1\ 4/2\ 4/3
4/4\ 4/5\ 4/6\ 4/7
} Block mosaics \(em {
\fB5/4\fR
\ 5/1\ 5/2\ 5/3
5/4\ 5/5\ 5/6\ 5/7
}
_
.T&
cw(54p) | cw(36p) | cw(48p) | cw(54p) | cw(36p) | cw(48p) .
Contiguous Row start 5/9 5/9 Separated 5/10 5/10
_
Unable to convert table
.TE
.nr PS 9
.RT
.ad r
\fBTable 1/T.100 [T1.100], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
\fBrepeat (RPT, coded 1/2)\fR
.sp 9p
.RT
.LP
\fIF:\ r\*'ep\*'etition (RPT)\fR
.LP
\fIS:\ repetici\*'on (RPT)\fR
.PP
This code indicates that the preceding graphics
character is to be repeated. The number of repetitions is indicated in
binary form by the six least significant bits of the subsequent character
chosen from columns\ 4 to\ 7. The character itself is not included in the
count. This
function does not apply to control characters.
.RT
.PP
5.4.1.3
A supplementary set of 32 controls, of which 31 have been
allocated, are coded as a C1\ set (see Figure\ 7/T.100). The attributes
defined by such controls become a property of the active position and move
with it
under the action of format effectors or spacing display characters.
.sp 9p
.RT
.PP
5.4.1.4
The mosaic repertoire is coded as a G1 set, of which several
representations may be defined (see Figure\ 8/T.100).
.sp 2P
.LP
5.4.2
\fIDisplay control functions\fR
.sp 1P
.RT
.PP
5.4.2.1
The display control functions are of two kinds depending on the range of
their action:
.sp 9p
.RT
.LP
\(em
\fIDefined display area attributes\fR apply to individual character locations.
Their action is limited to zones separated
by APA\ functions.
.LP
\(em
\fIFull screen attributes\fR apply to the full screen
area and are taken as default values for defined display area
attributes.
.PP
The defined display area attributes are coded as functions from
the supplementary set of control functions (see Figure\ 7/T.100), with two
character escape sequences.
.PP
The full screen attribute is coded as a function from the
supplementary set of control functions with four character escape sequences
(see \(sc\ 5.4.2.3).
.RT
.PP
5.4.2.2
Attributes for use in the defined display area are as
follows.
\v'3p'
.sp 9p
.RT
.LP
5.4.2.2.1
Black\ foreground
\(rt
.LP
Red\ foreground
|
.LP
Green\ foreground
|
.LP
Yellow\ foreground
|
\(rk
.LP
Blue\ foreground
|
.LP
Magenta\ foreground
|
.LP
Cyan\ foreground
|
.LP
White\ foreground
\(rb
.LP
\-v'3P'
\-v'9p'
Causes the following
characters to be written
in the colour indicated.
\v'2P'
\v'11p'
.sp 1P
.LP
5.4.2.2.2
\fIFlashing\fR
.sp 9p
.RT
.PP
This control function causes the characters following it to be
displayed alternatively as they would otherwise be displayed, and as spaces,
under the control of a timing device in the receiver.
.RT
.sp 1P
.LP
5.4.2.2.3
\fISteady
.sp 9p
.RT
.PP
This control function causes the action of \fIflashing\fR to be
stopped.
.RT
.sp 1P
.LP
5.4.2.2.4
\fIStart box\fR
.sp 9p
.RT
.PP
This control function causes the characters following it to be
inset or added to a television picture, when the receiver is in the user's
control. (For further study.)
.RT
.sp 1P
.LP
5.4.2.2.5
\fIEnd box\fR
.sp 9p
.RT
.PP
This control function causes the action of \fIstart box\fR to be
stopped. (For further study.)
.RT
.sp 1P
.LP
5.4.2.2.6
\fINormal size\fR
.sp 9p
.RT
.PP
This control function causes the characters following it to occupy one
character position each.
.bp
.RT
.LP
.rs
.sp 47P
.ad r
\fBFigure 7/T.100, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 8/T.100, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
5.4.2.2.7
\fIDouble height\fR
.sp 9p
.RT
.PP
This control function causes the characters following it to occupy each
its active position and the corresponding position on the previous row.
(The origin of a character is the bottom left corner of the character
position.)
.RT
.sp 1P
.LP
5.4.2.2.8
\fIDouble width\fR
.sp 9p
.RT
.PP
This control function causes the characters following it to occupy two
consecutive character positions on the same row, and the active position
to be moved two positions forward with every character.
.RT
.sp 1P
.LP
5.4.2.2.9
\fIDouble size\fR
.sp 9p
.RT
.PP
This control function causes the characters following it to occupy the
active position, the next on the row and the two corresponding character
positions on the previous row. The active position is moved two character
positions forward with every character.
\v'5p'
.RT
.LP
5.4.2.2.10
Black\ background
.LP
Red\ background
.LP
Green\ background
.LP
Yellow\ background
.LP
Blue\ background
.LP
Magenta\ background
.LP
Cyan\ background
.LP
White\ background
.LP
\-v'4P'
\-v'2p'
Causes the following
characters to be displayed in their foreground
colour on a background of the colour
indicated.
\v'2P'
\v'6p'
.sp 1P
.LP
5.4.2.2.11
\fITransparent background\fR
.sp 9p
.RT
.PP
This control function causes the characters following it to
be displayed with a transparent background. This means the area not occupied
by the foreground colour takes the underlying background colour. This may
be one of the eight colours or the video picture as defined by the off
screen
attributes.
.RT
.sp 1P
.LP
5.4.2.2.12
\fIConceal display\fR
.sp 9p
.RT
.PP
This control function causes the characters following it, in the
same unit although stored in the receiver, to be displayed as spaces until
the user chooses to reveal them.
.RT
.sp 1P
.LP
5.4.2.2.13
\fIStop conceal\fR
.sp 9p
.RT
.PP
This control function causes the action of \fIconceal display\fR to be
stopped.
.RT
.sp 1P
.LP
5.4.2.2.14
\fIStart lining\fR
.sp 9p
.RT
.PP
This control function causes the characters following in the same unit
to be lined. The shape of lining may be different depending on the
character set used. In the case of the mosaic set, the lining causes the six
cells to be separated with a background boundary.
.RT
.sp 1P
.LP
5.4.2.2.15
\fIStop lining\fR
.sp 9p
.RT
.PP
This control function causes the action of \fIstart lining\fR to be
stopped.
.RT
.sp 1P
.LP
5.4.2.2.16
\fINormal polarity\fR
.sp 9p
.RT
.PP
This control function causes the action of \fIinverted polarity\fR to be
stopped.
.RT
.sp 1P
.LP
5.4.2.2.17
\fIInverted polarity\fR
.sp 9p
.RT
.PP
This control function causes the characters following it, in the
same unit, to be displayed as if the background and the foreground colour
have been exchanged. In the flashing attribute, the polarity of the flashing
clock is also inverted.
.RT
.sp 2P
.LP
5.4.2.3
\fIFull\(hyscreen attributes\fR
.sp 1P
.RT
.sp 1P
.LP
5.4.2.3.1\ \ Full\(hyscreen attributes apply for the total display period and
include the border area. In addition, provisions are made for full\(hyrow
attributes, applying for the entire row including the border area related to
that row.
.bp
.sp 9p
.RT
.PP
Full\(hyscreen attributes display controls are represented by four
character \fIEscape\fR sequences of the form ESC\ 2/3\ 2/0\ F\de\uwhere\
F\de\uis taken from Figure\ 7/T.100.
.PP
Full\(hyrow attributes display controls are represented by four\(hycharacter
\fIEscape\fR sequences of the form ESC\ 2/3\ 2/1\ F\de\u.
.RT
.sp 1P
.LP
5.4.2.3.2\ \ The following full\(hyscreen attributes need precise
definition:
.sp 9p
.RT
.LP
\(em
\fITransparent background:\fR \ The full\(hyscreen area is occupied by
a picture, which may not be part of the Videotex service
(e.g.\ a television picture). Non\(hyconcealed characters
appear on this picture. If they are also displayed with
defined display area transparent background, only the foreground
appears over the picture. Concealed characters are
displayed as transparent spaces.
.LP
\(em
\fIConceal:\fR \ The defined display area is in the full\(hyscreen
background colour until the user chooses to reveal it or
until this attribute is stopped by full\(hyscreen stop conceal.
.LP
\(em
\fIFull\(hyscreen stop conceal:\fR \ This has the same action as the
action of the user on the reveal key.
.sp 1P
.LP
5.4.2.3.3\ \ For row\(hydefined full\(hyscreen attributes, the following may
also apply:
.sp 9p
.RT
.LP
\(em
lined;
.LP
\(em
double width;
.LP
\(em
double height.
.sp 2P
.LP
5.4.3
\fICoding of the mosaic repertoire\fR
.sp 1P
.RT
.PP
5.4.3.1
The mosaic repertoire is designated as a G1 set invoked by the SO function.
Two alternative
fonts
(contiguous and separated) are
proposed. The separated font is obtained by applying the lining attribute
applied to the mosaic set. The mosaic set code table is given in Figure\
8/T.100 together with examples of the fonts.
.sp 9p
.RT
.sp 2P
.LP
5.4.4
\fIDefault conditions\fR
.sp 1P
.RT
.sp 1P
.LP
5.4.4.1
\fIDefault full\(hyscreen attributes\fR
.sp 9p
.RT
.PP
At the beginning of a display frame
(initiated by function\ CS) the default conditions for full\(hyscreen attributes
are set at white foreground, black background, single size, unboxed, revealed,
steady, non\(hylined.
.RT
.sp 1P
.LP
5.4.4.2
\fIDefault defined display area attributes\fR
.sp 9p
.RT
.PP
After functions directly
addressing a character location on the screen (APH or APA function) the
defined display area attributes are reset to the value of the current full\(hyscreen
attributes.
.RT
.sp 1P
.LP
5.4.4.3
\fIDefault full\(hyrow attributes\fR
.sp 9p
.RT
.PP
The default condition of full\(hyrow attributes is the current value of
full\(hyscreen attributes.
.RT
.LP
\fB6\fR \fBAlphageometric option\fR
.sp 1P
.RT
.sp 2P
.LP
6.1
\fIGeneral\fR
.sp 1P
.RT
.sp 1P
.LP
6.1.1
\fIDescription\fR \v'3p'
.sp 9p
.RT
.PP
6.1.1.1
In the alphageometric option, the display is composed of
alphanumeric texts and pictorial drawings that are defined in terms of
geometric primitives transmitted to the terminal as drawing commands.
.PP
6.1.1.2
One coding scheme for the alphageometric option for Videotex is
described in \(sc\ 6.
.bp
.sp 2P
.LP
6.1.2
\fIDesignation and invocation of geometric codes\fR
.sp 1P
.RT
.PP
6.1.2.1
The designation and invocation of the alphageometric code is
specified in \(sc\ 2.3.
.sp 9p
.RT
.PP
The occurrence of the control function SO invokes the geometric
primitives in code table positions\ 2/0 to\ 7/15 inclusive. The occurrence
of the code function\ SI re\(hyestablishes the G0\ set and the \fIspace\fR
\ (2/0) and
\fIdelete\fR \ (7/15) functions.
.sp 2P
.LP
6.1.3
\fIGeometric primitives\fR
.sp 1P
.RT
.PP
6.1.3.1
The coding scheme for the G1 set together with the code
positions 2/0 and 7/15 for the geometric model is based on
geometric primitives. Each drawing primitive is specified in terms of Cartesian
coordinates to describe the positions, end\(hypoints, or vertices of each
drawing operation.
.sp 9p
.RT
.PP
6.1.3.2
Geometric drawings are defined in terms of the drawing
primitives: \fIpoint\fR , \fIline\fR , \fIarc\fR , \fIrectangle\fR , and
\fIpolygon\fR .
.sp 2P
.LP
6.1.4
\fIDrawing position\fR
.sp 1P
.RT
.PP
6.1.4.1
Drawings are positionally independent; therefore drawing
primitives may overlay each other redefining the drawing at the position.
.sp 9p
.RT
.sp 2P
.LP
6.1.5
\fIDrawing space\fR
.sp 1P
.RT
.PP
6.1.5.1
Space for geometric drawing operations consists of a
rectangular area entirely visible on the display screen. Any area of the
display screen outside of the valid drawing area is termed a \fIborder
area\fR and it is not possible to specify a coordinate position in a border
area.
.sp 9p
.RT
.sp 2P
.LP
6.1.6
\fIPicture element\fR
.sp 1P
.RT
.PP
6.1.6.1
The Cartesian coordinate grid is made up of square picture
elements (pixels).
.sp 9p
.RT
.sp 2P
.LP
6.1.7
\fIPicture resolution\fR
.sp 1P
.RT
.PP
6.1.7.1
Any number of picture elements may be implemented. Hence,
picture resolution is at the discretion of terminal manufacturers.
.sp 9p
.RT
.sp 2P
.LP
6.1.8
\fICoordinate system\fR
.sp 1P
.RT
.PP
6.1.8.1
The coordinate specifications are defined based on a
Cartesian\ 0 to\ 1 numbering scheme.
.sp 9p
.RT
.PP
6.1.8.2
The numbering system is referenced to the visible valid drawing
area and consists of coordinates ranging from\ 0 to\ 1 on both the\ X and\
Y axes, with coordinate values being specified as fractions of this range.
.PP
6.1.8.3
The coordinates are encoded in 2's complement notation and
specified as signed numbers to a minimum accuracy of 9\ bits, including
the sign bit. Increased accuracy is obtained by additional increments of
3\ bits. Unused least significant bits are truncated when the coordinates
are defined to a
greater accuracy than can be handled by the terminal.
.PP
6.1.8.4
Display screens with non\(hysquare visible areas map into the
square drawing area number system so that the origin (0,0) remains in the
lower left\(hyhand corner. On a television\(hylike display with a\ 4 | |
aspect ratio, this corresponds to a range of\ 0 to\ 0.999\ . | | in the\
X axis and\ 0 to
approximately\ 0.75 in the\ Y axis. Drawing commands addressing the entire
square\ 0 to\ 1 grid are permissible, but only the circumscribed\ 4 | |
area is
visible.
.sp 2P
.LP
6.2
\fIDrawing command\fR
.sp 1P
.RT
.sp 1P
.LP
6.2.1
\fIGeneral\fR
.sp 9p
.RT
.PP
6.2.1.1
Drawing commands consist of \fIoperational codes\fR (opcodes) and their
associated data parameters.
.bp
.sp 9p
.RT
.PP
6.2.1.2
Opcodes
describe the types of drawing operation.
.PP
6.2.1.3
Following the opcode byte are one or more blocks of additional
bytes of data to describe one or more (X,\ Y) coordinate positions. Each
block of data for the (X,\ Y) coordinates may contain 3\ bytes (9\ bits
accuracy),
4\ bytes (12\ bits accuracy),\ etc., depending on the degree of resolution
desired.
.PP
6.2.1.4
Figure 9/T.100 is the code table for the opcodes and data bytes
or status sub\(hycommands.
.sp 2P
.LP
6.2.2
\fIOpcode byte\fR
.sp 1P
.RT
.PP
6.2.2.1
The structure of the opcode byte is as shown in
Figure\ 10/T.100.
.sp 9p
.RT
.sp 2P
.LP
6.2.3
\fIOpcode definitions\fR
.sp 1P
.RT
.sp 1P
.LP
6.2.3.1
\fIPoint\fR
.sp 9p
.RT
.PP
Sets the drawing beam to any position in the display space and
optionally draws a point.
.RT
.sp 1P
.LP
6.2.3.2
\fILine\fR
.sp 9p
.RT
.PP
Draws a line based on the two given end points.
.RT
.sp 1P
.LP
6.2.3.3
\fIArc\fR
.sp 9p
.RT
.PP
Draws a circular arc based on three points, which are the start
point, a point on the arc and the end point of the arc. A circle results
when the start and end points are coincidental and the point on the arc
defines the opposite end of the diameter. The arc may be either in outline
or the area
enclosed by the arc and the chord may be filled.
.RT
.sp 1P
.LP
6.2.3.4
\fIRectangle\fR
.sp 9p
.RT
.PP
Draws a rectangle based on specified width and height. The
rectangle may be in outline or a filled\(hyin area.
.RT
.sp 1P
.LP
6.2.3.5
\fIPolygon\fR
.sp 9p
.RT
.PP
Draws a closed polygon of arbitrary shape specified by the
vertices. The polygon may be in outline or a filled\(hyin area. The maximum
number of vertices is limited to\ 256.
.RT
.sp 1P
.LP
6.2.3.6
\fISpare\fR
.sp 9p
.RT
.PP
An opcode available for future definition.
.RT
.sp 1P
.LP
6.2.3.7
\fIReserved\fR
.sp 9p
.RT
.PP
An opcode reserved for a specific future application.
.RT
.sp 1P
.LP
6.2.3.8
\fIControl\fR
.sp 9p
.RT
.PP
Provides control over the modes or attributes of the drawing
commands.
.RT
.sp 2P
.LP
6.2.4
\fIOpcode facilities\fR
.sp 1P
.RT
.PP
6.2.4.1
Each opcode has four variants; these are defined by the
facility bits\ (b2 and\ b1) as shown in
Figure\ 11/T.100. Facility field
interpretations are as given below.
.bp
.sp 9p
.RT
.LP
.rs
.sp 47P
.ad r
\fBFigure 9/T.100 p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 11P
.ad r
\fBFigure 10/T.100, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 31P
.ad r
\fBFigure 11/T.100 [T2.100], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
6.2.4.2
\fIb2 is binary 1\fR
.sp 9p
.RT
.LP
a)
\fIPoint\fR \ \(em\ A visible point is drawn on the display screen.
.LP
b)
\fILine, arc, rectangle, polygon\fR \ \(em\ The initial drawing
position is specified within the data bytes as absolute (X,\ Y) coordinates,
i.e.\ the initial point is \fIset\fR .
.sp 1P
.LP
6.2.4.3
\fIb2 is binary 0\fR
.sp 9p
.RT
.LP
a)
\fIPoint\fR \ \(em\ An invisible point is located on the display
screen.
.LP
b)
\fILine, arc, rectangle, polygon\fR \ \(em\ The initial drawing
position is the same point as the final drawing position of the
previous opcode, i.e.,\ the current drawing is
joined to the previous drawing.
.sp 1P
.LP
6.2.4.4
\fIb1 is binary 1\fR
.sp 9p
.RT
.LP
a)
\fIPoint\fR \ \(em\ The (X, Y) coordinates are relative displacements
to the preceding coordinate specifications.
.LP
b)
\fILine\fR \ \(em\ The (X, Y) coordinates for the final drawing
position of a line segment are relative displacements from
initial drawing position of that line segment.
.LP
c)
\fIArc, rectangle, polygon\fR \ \(em\ The areas established are filled
or crosshatched.
.sp 1P
.LP
6.2.4.5
\fIb1 is binary 0\fR
.sp 9p
.RT
.LP
a)
\fIPoint\fR \ \(em\ The (X, Y) coordinates of the point are absolute values.
.LP
b)
\fILine\fR \ \(em\ The (X, Y) coordinates of the final drawing
position of the line segment are absolute values.
.LP
c)
\fIArc, rectangle, polygon\fR \ \(em\ The drawings are
outlined.
.sp 2P
.LP
6.3
\fIOpcode numeric data\fR
.sp 1P
.RT
.PP
6.3.1
The numerical data bytes associated with an opcode immediately follow the
opcode byte and are recognized when the flag bit\ (b7) is binary\ 1. Any
number of blocks of data bytes defining pairs of coordinates or drawing
displacements may follow the drawing opcode until one of the following
conditions occurs:
.sp 9p
.RT
.LP
a)
when another opcode is encountered;
.LP
b)
when the \fIshift\(hyin\fR code (SI) is encountered;
.LP
c)
when the \fIshift\(hyout\fR code (SO) is encountered;
.LP
d)
when the \fIsingle\(hyshift\fR codes (SS2 or SS3) are encountered;
.LP
e)
when an \fIescape\fR (ESC) code is encountered.
.PP
6.3.2
The minimum number of data bytes that forms a block that
defines a pair of\ X,\ Y coordinates is three. The structure of the data
block is shown in Figure\ 12/T.100.
.sp 9p
.RT
.LP
.rs
.sp 14P
.ad r
\fBFigure 12/T.100 p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
6.4
\fIRepeated opcode operation\fR
.sp 1P
.RT
.PP
6.4.1
For each of the \fIpoint\fR , \fIline\fR and \fIrectangle\fR opcodes,
repeated drawing operations will automatically be effected if the numerical
data field following the opcode byte contains more than one complete set of
coordinate specifications. A complete set of coordinate specifications is
defined as all the coordinates needed to define a \fIpoint\fR , \fIline\fR or
\fIrectangle\fR drawing as a single drawing. That is, the repeated drawing
feature allows concatenated drawings to be effected without having to repeat
the opcode itself.
.sp 9p
.RT
.sp 2P
.LP
6.5
\fIGeometric control opcode\fR
.sp 1P
.RT
.sp 1P
.LP
6.5.1
\fIGeneral\fR
.sp 9p
.RT
.PP
6.5.1.1
The \fIcontrol\fR opcodes control the drawing states of the
terminal and the interpretation of the drawing opcode attributes. The sequence
of \fIcontrol\fR opcodes and their \fIstatus\fR sub\(hycommands always
precedes the
opcodes for the geometric drawing primitives of \fIpoint\fR , \fIline\fR
, \fIarc\fR ,
\fIrectangle\fR , or \fIpolygon\fR . The controls also apply to text in
\fIshift\(hyin\fR \ (SI) mode. The four \fIcontrol\fR opcodes, distinguished
by the opcode facilities bits, (b2\ and\ b1), are given in Figure\ 13/T.100.
.sp 9p
.RT
.LP
.rs
.sp 16P
.ad r
\fBFigure 13/T.100 p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
6.5.1.2
\fIControl (value)\fR
.sp 9p
.RT
.PP
This control opcode defines the colour or grey scale accessed by
subsequent drawing opcodes.
.RT
.sp 1P
.LP
6.5.1.3
\fIControl (status)\fR
.sp 9p
.RT
.PP
This control opcode provides extension to a field of
sub\(hycommands.
.RT
.sp 1P
.LP
6.5.1.4
\fIControl (reserved)\fR
.sp 9p
.RT
.PP
This control opcode is reserved for future control commands.
.RT
.sp 1P
.LP
6.5.1.5
\fIControl (private)\fR
.sp 9p
.RT
.PP
This control opcode is reserved for use by terminal manufacturers to implement
proprietary non\(hystandard functions.
.bp
.RT
.sp 2P
.LP
6.5.2
\fIAttributes\fR
.sp 1P
.RT
.PP
6.5.2.1
A number of drawing attributes may be applied to the drawing
commands. Attributes are defined by appropriate coded sequences as described
below. Once an attribute is defined, it remains valid until the attribute is
redefined.
.sp 9p
.RT
.PP
6.5.2.2
In the implementation of attributes, the level of sophistication and complexity
is left to the discretion of the implementer.
.PP
6.5.2.3
For the different drawing attributes and their feature levels
see Recommendation\ F.300.
.sp 2P
.LP
6.5.3
\fIControl (value)\fR
.sp 1P
.RT
.PP
6.5.3.1
This opcode specifies the colour attribute or grey scale value of the drawings
(or text) that follow. Whether the \fIcontrol (value)\fR opcode and its
associated data bytes contain colour or grey scale information, is
predetermined by the \fItonal\fR status sub\(hycommand (see \(sc\ 6.5.4).
The number of
data bytes is variable and the sequence is terminated on the appearance of
another opcode. Less significant bits for colour or grey scale information
are truncated where they are not used. The bit assignments of the data
bytes are
shown in Figure\ 14/T.100 (only the 6\(hybit data portion of the 8\(hybit byte
is shown).
.sp 9p
.RT
.LP
.rs
.sp 17P
.ad r
\fBFigure 14/T.100 p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
6.5.4
\fIControl (status) and status sub\(hycommands\fR
.sp 1P
.RT
.PP
6.5.4.1
The \fIcontrol (status)\fR opcode accesses a field of \fIstatus\fR
\fIsub\(hycommands\fR (columns\ 4, 5, 6 and\ 7) which define in detail
all the modes of drawing operation or attributes. The sequence is always
\fIcontrol (status)\fR
followed by a \fIstatus sub\(hycommand\fR , which in turn may or may not
be further
followed by parameter data bytes. Figure\ 15/T.100 gives the codings of the
\fIstatus sub\(hycommands\fR . Detailed definitions of the \fIstatus sub\(hycommands\fR
are
given below.
.sp 9p
.RT
.sp 1P
.LP
6.5.4.2\ (4/0)
\fIClear\(hyto\(hyblack\fR
.sp 9p
.RT
.PP
This sub\(hycommand clears the entire display to black.
.RT
.sp 1P
.LP
6.5.4.3\ (4/1)
\fIClear\(hyto\(hytransparent\fR
.sp 9p
.RT
.PP
This sub\(hycommand clears the entire display of the screen
to transparent. By transparent is meant that conventional television pictures
can be mixed with Videotex images or text.
.bp
.RT
.sp 1P
.LP
6.5.4.4\ (4/2)
\fIClear\(hyto\(hyblack and initialize\fR
.sp 9p
.RT
.PP
This sub\(hycommand clears the entire display to black and resets the terminal
to the default mode.
.RT
.sp 1P
.LP
6.5.4.5\ (4/3)
\fIClear\(hyto\(hycurrent colour\fR
.sp 9p
.RT
.PP
This sub\(hycommand clears the entire display to
the colour currently specified by the \fIcontrol (value)\fR opcode
sequence.
.RT
.sp 1P
.LP
6.5.4.6\ (4/4)
\fIDomain (3 bytes)\fR
.sp 9p
.RT
.PP
The block of numerical data that follows an opcode contains
3\ bytes. This is also the default condition.
.RT
.sp 1P
.LP
6.5.4.7\ (4/5)
\fIDomain (4 bytes)\fR
.sp 9p
.RT
.PP
The block of numerical data that follows an opcode contains
4\ bytes.
.RT
.sp 1P
.LP
6.5.4.8\ (4/6)
\fIDomain (5 bytes)\fR
.sp 9p
.RT
.PP
The block of numerical data that follows an opcode contains
5\ bytes.
.RT
.sp 1P
.LP
6.5.4.9\ (4/7)
\fIDomain (6 bytes)\fR
.sp 9p
.RT
.PP
The block of numerical data that follows an opcode contains
6\ bytes.
.RT
.sp 1P
.LP
6.5.4.10\ (4/8)
\fIDrawing (blink\(hyoff)\fR
.sp 9p
.RT
.PP
Terminates the drawing (blink\(hyon) status sub\(hycommand.
.RT
.sp 1P
.LP
6.5.4.11\ (4/9)
\fIReserved\fR
.sp 9p
.RT
.sp 1P
.LP
6.5.4.12\ (4/10)
\fIDrawing (blink\(hyon) (or flashing)\fR
.sp 9p
.RT
.PP
This sub\(hycommand causes the drawing (or
text) that follows to flash in a repetitive manner for the purpose of drawing
attention. In general, an object of any colour or grey scale may be blinked,
but in some implementations, blinking may be restricted.
.RT
.sp 1P
.LP
6.5.4.13\ (4/11)
\fIReserved\fR
.sp 9p
.RT
.sp 1P
.LP
6.5.4.14\ (4/12)
\fITonal (colour)\fR
.sp 9p
.RT
.PP
This sub\(hycommand designates that the
\fIControl (value)\fR sequence carries colour information (see \(sc\ 6.5.3).
.RT
.sp 1P
.LP
6.5.4.15\ (4/13)
\fITonal (grey scale)\fR
.sp 9p
.RT
.PP
This sub\(hycommand designates that the \fIControl\fR \fI(value)\fR sequence
carries grey scale information (see \(sc\ 6.5.3).
.RT
.sp 1P
.LP
6.5.4.16\ (4/14)
\fIReserved\fR
.sp 9p
.RT
.sp 1P
.LP
6.5.4.17\ (4/15)
\fIReserved\fR
.sp 9p
.RT
.sp 1P
.LP
6.5.4.18\ (5/0)
\fILine (solid)\fR (See Note)
.sp 9p
.RT
.PP
This sub\(hycommand indicates that the drawing lines will be solid.
This is also the default condition.
.RT
.sp 1P
.LP
6.5.4.19\ (5/1)
\fILine (dotted)\fR (See Note)
.sp 9p
.RT
.PP
This sub\(hycommand indicates that the drawing lines will be dotted in texture.
.bp
.RT
.LP
.rs
.sp 47P
.ad r
\fBFigure 15/T.100, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
6.5.4.20\ (5/2)
\fILine (dashed)\fR (See Note)
.sp 9p
.RT
.PP
This sub\(hycommand indicates that the drawing lines will be dashed
in texture.
.RT
.sp 1P
.LP
6.5.4.21\ (5/3)
\fILine (dot\(hydashed)\fR (See Note)
.sp 9p
.RT
.PP
This sub\(hycommand indicates that the drawing lines will be
dot\(hydashed in texture.
.PP
\fINote\fR \ \(em\ The line texture pattern is referenced to the absolute
coordinate grid of the display screen so that the texture pattern aligns
between drawing commands.
.RT
.sp 1P
.LP
6.5.4.22\ (5/4)
\fIFill\fR
.sp 9p
.RT
.PP
This sub\(hycommand fills the enclosed
area drawn in the colour specified by the current \fIControl (value)\fR
sequence.
.RT
.sp 1P
.LP
6.5.4.23\ (5/5)
\fIReserved\fR
.sp 9p
.RT
.sp 1P
.LP
6.5.4.24\ (5/6)
\fIFill (border highlight black)\fR
.sp 9p
.RT
.PP
This sub\(hycommand fills enclosed area drawn
as \(sc\ 6.5.4.22 above and the circumscribing border is highlighted in black.
.RT
.sp 1P
.LP
6.5.4.25\ (5/7)
\fIReserved\fR
.sp 9p
.RT
.sp 1P
.LP
6.5.4.26\ (5/8)
\fIReserved\fR
.sp 9p
.RT
.sp 1P
.LP
6.5.4.27\ (5/9)
\fIReserved\fR
.sp 9p
.RT
.sp 1P
.LP
6.5.4.28\ (5/10)
\fIReserved\fR
.sp 9p
.RT
.sp 1P
.LP
6.5.4.29\ (5/11)
\fIReserved\fR
.sp 9p
.RT
.sp 1P
.LP
6.5.4.30\ (5/12)
\fIWait (timed)\fR
.sp 9p
.RT
.PP
This sub\(hycommand causes a delay of a specific time in processing
and display. The length of wait is specified in tenths of a second, either
by one associated parameter byte (6\ bits for up to 6.3\ s) or two parameter
bites (12\ bits for up to 6.8\ m).
.RT
.sp 1P
.LP
6.5.4.31\ (5/13)
\fIWait (indefinite)\fR
.sp 9p
.RT
.PP
This sub\(hycommand causes an indefinite wait. This may
be achieved by the terminal responding with a \fIpause flow\fR control
character
(DC3\ in C0\ set) towards the computer. The wait is then terminated when the
terminal sends a \fIresume data flow\fR character (DC1\ in C0\ set).
.RT
.sp 1P
.LP
6.5.4.32\ (5/14)
\fIReserved\fR
.sp 9p
.RT
.sp 1P
.LP
6.5.4.33\ (5/15)
\fIReserved\fR
.sp 9p
.RT
.sp 1P
.LP
6.5.4.34\ (6/0)
\fIText format\fR
.sp 9p
.RT
.PP
This sub\(hycommand has an associated data byte, which defines the
text formats as follows:
.RT
.LP
Bit\ b6\ =\ 0:
Free format, i.e. character strings are wrapped around
on the right margin.
.LP
Bit\ b6\ =\ 1:
Annotation format, i.e. character strings are in fixed
positions on the screen.
.LP
Bit\ b5\ =\ 0:
In free format, character strings are broken on a
character boundary.
.LP
Bit\ b5\ =\ 1:
In free format, character strings are broken on a word
boundary.
.LP
b4,\ b3:
Defines character rotation as shown in Figure 16/T.100.
Rotated strings of characters proceed in the direction
of rotation. However, all other format controls on
characters such as APB, APF, APD, APU and APR have
their (unrotated) orientation meanings.
.LP
b2,\ b1\ =\ 0.0:
Vertical spacing\ =\ 1.0
.LP
b2,\ b1\ =\ 0.1:
Vertical spacing\ =\ 1.5
.LP
b2,\ b1\ =\ 1.0:
Vertical spacing\ =\ 2.0
.LP
b2,\ b1\ =\ 1.1:
Vertical spacing\ =\ 2.5
.bp
.LP
.rs
.sp 11P
.ad r
\fBFigure 16/T.100 p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
6.6
\fIDefault conditions\fR
.sp 1P
.RT
.PP
6.6.1
The default conditions of the attributes for the alphageometric coding
scheme are summarized below:
\v'3p'
.sp 9p
.RT
.LP
Reference
.LP
1)
Control\ (value):
White
\(sc\ 6.5.3
.LP
2)
Tonal\ control:
Tonal (colour)
\(sc\ 6.5.4.14
.LP
3)
Domain:
3 bytes (9 bits)
\(sc\ 6.5.4.6
.LP
4)
Drawing:
Blink\(hyoff
\(sc\ 6.5.4.10
.LP
5)
Line\ control:
Solid line
\(sc\ 6.5.4.18
.LP
6)
Fill:
Solid fill
.LP
(no highlight)
\(sc\ 6.5.4.22
.LP
7)
Text\ format:
a)\ Free format
\(sc\ 6.5.4.34
.LP
b)\ Break on character boundary
\(rt
\ with bits 1
.LP
c)\ No rotation
\(rk
\ to 6 set to \*Q0\*U
.LP
d)\ Vertical spacing = 1.0
\(rb
.sp 2P
.LP
\fB7\fR \fBAlpha\(hydynamically redefinable character sets (DRCS)\fR
\fBoption\fR
.sp 1P
.RT
.sp 1P
.LP
7.1
\fIGeneral\fR
.sp 9p
.RT
.PP
7.1.1
A DRCS is a set of characters whose shapes are sent from the
data\(hybase and down\(hyloaded via the line. It may be used to represent
alphabetic characters, special symbols, or picture element symbols for
constructing fine graphics. Once loaded, the DRCS are regarded as members
of a library that can be designated by appropriate\ ESC sequences as G0,
G1, G2, G3\ sets. Several
schemes for the DRCS option are possible. One scheme is described in \(sc\ 7
in the context of a general architecture. When used in its alphanumeric
mode DRCS may be employed as a part of the alphabetic representations of any
other Videotex option and in that case, the attributes associated with that
option are to be used.
.sp 9p
.RT
.sp 2P
.LP
7.2
\fIGeneral architecture for\fR
\fIdown\(hyloading DRCS\fR
.sp 1P
.RT
.sp 1P
.LP
7.2.1
\fIInitiation\fR
.sp 9p
.RT
.PP
The down\(hyloading process is initiated by
a designation and invocation sequence. This sequence is followed by one
or more of the following functions.
.bp
.RT
.sp 1P
.LP
7.2.2
\fIIdentification of character set (ICS)\fR
.sp 9p
.RT
.PP
This function must immediately follow the initiating sequence. It identifies
the \fIescape\fR sequence used for the designation of the character
set.
.RT
.sp 1P
.LP
7.2.3
\fISelect coding method (SCM)\fR
.sp 9p
.RT
.PP
This function defines the type of coding used to describe the DRCS character.
.RT
.sp 1P
.LP
7.2.4
\fISelect dot composition (SDC)\fR
.sp 9p
.RT
.PP
This function defines the number
of bits horizontally and vertically in a character matrix, the number of
bits per pixel, the number of grey scale levels and the number of colours
accessible within a character position.
.RT
.sp 1P
.LP
7.2.5
\fIPattern transfer (PT)\fR
.sp 9p
.RT
.PP
This is the active part of the down\(hyloading process. It defines the
code location of the first character and provides instructions and data
to draw characters. It may also incorporate an error checking procedure.
.RT
.sp 1P
.LP
7.2.6
\fIDown\(hyloading termination procedure (DLT)\fR
.sp 9p
.RT
.PP
The down\(hyloading process is terminated by a specific procedure,
which may include acknowledgement.
.RT
.sp 2P
.LP
7.3
\fIA possible coding scheme for the DRCS option\fR
.sp 1P
.RT
.sp 1P
.LP
7.3.1
\fIInitiating sequence\fR
.sp 9p
.RT
.PP
The initiating sequence is ESC F\ds\ufollowed by \fIx\fR \ bytes
indicating the length of the loading data block, where\ \fIx\fR is for further
study.
.RT
.sp 1P
.LP
7.3.2
\fITermination procedure\fR
.sp 9p
.RT
.PP
The down\(hyloading process is terminated by means of counting the
length of the loading data block. See \(sc\ 7.3.1.
.RT
.sp 2P
.LP
7.3.3
\fIDesignation and invocation of loaded DRCS\fR
.sp 1P
.RT
.PP
7.3.3.1
Once loaded into the terminal, the DRCS is placed into a
library. This library is used in the context of ISO\ 2022 in the 7\(hybit
environment as implemented in earlier sections. Before invoking the designated
DRCS, it is required to designate a\ C1 set to be associated with it. For
the
scheme described herein any of the C1\ sets (to be registered) that are
defined in \(sc\(sc\ 2.2 and\ 2.3 may be used.
.sp 9p
.RT
.PP
7.3.3.2
The designation sequence will be of the form ESC I\d1\u, 2/0,
(I\d3\u\ . | | \ I\dn\u)\ F. I\d1\u\ will be\ 2/8,\ 2/9,\ . | | \ or\ 2/15.
I\d3\u\ . | |
\ I\dn\uare optional, and if present together with\ F, will
identify the set. Means for associating the designating sequence with the
process of defining the character shapes will be for further study.
.sp 9p
.RT
.sp 2P
.LP
\fB8\fR \fBAlphaphotographic option\fR
.sp 1P
.RT
.PP
8.1
The alphaphotographic option is used to render an image by the transmission
and display of individual picture elements.
.sp 9p
.RT
.PP
8.2
This option may include both continuous\(hytone images such as
pictures of faces,\ etc., as well as pattern\(hyoriented techniques for
the display of pictures, including graphics, Latin and non\(hyLatin characters
for text,\ etc. The system features and attributes include colour and monochrome.
.PP
8.3
The detailed system proposals are for further study.
.bp
.sp 2P
.LP
\fB9\fR \fBService enhancements\fR
.sp 1P
.RT
.sp 1P
.LP
9.1
\fIIntroduction\fR
.sp 9p
.RT
.PP
9.1.1
Many Administrations are offering or considering the
introduction of a Videotex service, and it is recognized that this
Recommendation may influence some of their decisions. While the other sections
of this Recommendation contain details of those aspects of an international
Videotex service that could be agreed upon, this \(sc\ 9 identifies certain
potential enhancements (features or attributes) that some Administrations
believe need to be considered in future developments.
.sp 9p
.RT
.PP
9.1.2
It is recognized that some of these potential enhancements may
only exist on national Videotex services, while others may have international
application. However, an enhancement that begins on a national service
only
could become international in the future. Therefore, it is considered desirable
to have international coordination of future enhancements.
.sp 2P
.LP
9.2
\fIGeneral\fR
.sp 1P
.RT
.PP
9.2.1
The growth of international Videotex services during the years following
the publication of this Recommendation will be greatly affected by
the specific specifications contained in the other parts of this
Recommendation. However, some Administrations believe that experiments with
and/or implementation of certain enhancements will allow the development
of an international service that provides a range of capabilities that
will maximize the desirability and utilization of Videotex service.
.sp 9p
.RT
.PP
9.2.2
Some of the potential enhancements to Videotex service,
national or international, are presented in the following. This is for the
purpose of identifying to interested Administrations those enhancements that
warrant serious consideration in the view of the CCITT, but which presently
lack enough details to obtain the full agreement of all
Administrations.
.PP
9.2.3
The enhancements have been grouped into three categories in
order to assist the reader in understanding the application of each individual
enhancement (which may be referred to by some Administrations as attributes
or features or some other descriptive phrase) and to prompt an orderly
investigation of them:
.LP
a)
display\(hyrelated enhancements;
.LP
b)
transmission\(hyoriented enhancements;
.LP
c)
system level enhancements.
.sp 2P
.LP
9.3
\fIDisplay related enhancements\fR
.sp 1P
.RT
.PP
9.3.1
Most of the currently planned and/or offered services utilize images created
with only eight colours, which are formed by the various
combinations (on or off) of three primary colours\ \(em red, green and blue.
Limiting Videotex to eight colours is an unnecessary restriction, since the
electronic emission devices controlling the red, green and blue colours
can be caused to have more than just the two states of on or off. For example,
with
just eight different states or levels, a potential of 512\ colours exist.
Additionally, for those services that use a matrix\(hyoriented screen (e.g.\ a
mosaic graphic mode), different colours could be identified for foreground
symbols to those for background areas.
.sp 9p
.RT
.PP
9.3.2
The ability to simulate motion (i.e. animation) is a potential
enhancement that can be achieved by several means. These include:
.LP
a)
alternating between slightly different display frames
stored in the terminal;
.LP
b)
dynamically altering the colour of portions of the display image, making
them appear or disappear by redefining the
colour table (an image disappears when its colour is set
to the same colour as the surrounding area);
.LP
c)
execution of a resident program to redefine the image at a controlled rate.
.PP
9.3.3
The flashing of symbols or areas of the display has typically been
limited to changing the foreground symbol (in the case of a matrix\(hyoriented
screen) to the background colour, momentarily, or some other single\(hystate
change. An enhanced flashing capability could allow for different rates of
change and for various conditions associated with each change (e.g.\ colour\
X to colour\ Y, rather than foreground colour to background colour or foreground
colour to black).
.bp
.sp 9p
.RT
.PP
9.3.4
Different pictorial (text and graphic) symbols may be developed
that extend the repertoire of a Videotex service. This may be a fixed extension
defined in the terminal memory, or can be a modification to the existing
memory by downloading from the data base. The range of extended symbols
includes
different fonts of existing symbols, smoothed mosaic graphics, or other
unique symbols.
.sp 2P
.LP
9.4
\fITransmission oriented enhancements\fR
.sp 1P
.RT
.PP
9.4.1
The exchange of information directly between terminals, without communicating
with a Videotex service may be permitted by some Administrations as an
enhanced capability, and could be of value to the users of Videotex
terminals. Such a capability would require the existence of control functions
that might not, otherwise, be available in some terminals that utilize
certain existing or planned national Videotex services, but this should
not cause any incompatibilities with such services.
.sp 9p
.RT
.PP
9.4.2
The optimization of the coded character stream for maximum data
rate is a valuable enhancement. This might be accomplished by utilizing an
8\(hybit per word coding format rather than the 7\(hybit per word format
currently
planned by most Administrations, coupled with a related decision on the
line or link level protocol selected. The selection of an 8\(hybit per
word format could permit a more efficient transmission of data.
.PP
In addition, such techniques as run\(hylength\(hyencoding might be
specified in the Recommendation to reduce the transmission of unnecessary or
redundant data. The choice of higher speed modems/circuits is also considered
by some Administrations as a way to optimize the transfer of data within
or
between Videotex services.
.PP
9.4.3
For some applications of a Videotex service, sophisticated
error detection and correction schemes may be required and should be considered
with other transmission\(hyoriented enhancements on future Videotex services.
.sp 9p
.RT
.sp 2P
.LP
9.5
\fISystem level enhancements\fR
.sp 1P
.RT
.PP
9.5.1
An enhancement seriously considered by some Administrations is the provision
of a Videotex service that provides visual information, augmented by audio
information. This capability could permit access by a terminal to
visual\(hyonly information in a data base, and to visual/audio information
in the same or other data base. The audio information might be associated
with the
visual information, or treated separately, or even alternately, depending
upon the implementation. The audio information might be analogue or digitally
encoded or handled as a composite signal.
.sp 9p
.RT
.PP
9.5.2
The provisioning of peripheral input/output devices associated
with the Videotex terminal is an important enhancement for future services.
These could include magnetic storage devices for recording visual/audio
information as received by the terminal, or recorded locally by the terminal
for subsequent transmission to a data base or other terminal. Various hard
copy printing devices could also be provided, with their design based upon
the specific visual capabilities of the terminal, e.g.\ degree of resolution
and
colour of the image on the display screen.
.sp 2P
.LP
\fB10\fR \fBLine and end\(hyto\(hyend protocols\fR
.sp 1P
.RT
.PP
10.1
The purpose of \(sc\ 10 is to describe the protocols needed
for international Videotex transactions. Section\ 10 contains an introduction
only. Detailed consideration is left for further study.
.sp 9p
.RT
.PP
10.2
The transfer of information from a data base of one service to a user of
another service may be split up into two parts:
.sp 9p
.RT
.LP
a)
the information transfer from one service to another;
.LP
b)
the information transfer from the service to the
user.
.sp 2P
.LP
10.3
\fILine protocols\fR
.sp 1P
.RT
.sp 1P
.LP
10.3.1
\fILine protocols between services\fR
.sp 9p
.RT
.sp 1P
.LP
10.3.1.1\ \ The international line between national data base computers
must be able to transmit transparent coding schemes identified in this
Recommendation and accept the protocols of \(sc\ 10.4.
.bp
.sp 9p
.RT
.sp 2P
.LP
10.3.2
\fILine protocols between service and user\fR
.sp 1P
.RT
.sp 1P
.LP
10.3.2.1\ \ The following protocol functions should be studied:
.sp 9p
.RT
.LP
PF1:
Start of coded data starts a
sequence of data to be understood as textual information (could be coded as
STX).
.LP
PF2:
Start of prefix causes the
following bytes to be understood as a prefix containing framing information
including codes for error check and/or correction (could be coded as
SOH).
.LP
PF3:
End of coded data ends a sequence
of data to be understood as textual information (could be coded as ETX).
.LP
PF4:
End of frame. Ends a frame of
data and requests for reverse transmission and give an answer (could be
coded as ETB).
.LP
PF5:
Answer
given in case of error free reception or when error correction is possible
(could be coded as ACK).
.LP
PF6:
Answer given in case of errors
when no error correction is possible (could be coded as NAK).
.sp 1P
.LP
10.3.2.2\ \ It is noted that TC1 to TC10 (SOH to ETB of
Recommendation\ T.50) are intended to control the transmission of information
over transmission networks. The use of these functions may therefore not be
used as part of the information stream from one service to another.
.sp 9p
.RT
.sp 1P
.LP
10.3.2.3\ \ The use of protocol functions is for further study.
.sp 9p
.RT
.sp 2P
.LP
10.4
\fIProtocols for communication between services on the\fR
\fIapplication level\fR
.sp 1P
.RT
.sp 1P
.LP
10.4.1
\fIGeneral\fR
.sp 9p
.RT
.sp 1P
.LP
10.4.1.1\ \ International exchange of information between national
Videotex services may be sent in blocks, here called messages. For efficient
use of networks and communication equipment it is important to design the
messages to minimize the capacity needed for applications that are frequently
used in Videotex services.
.sp 9p
.RT
.sp 2P
.LP
10.4.2
\fITypes of message elements\fR
.sp 1P
.RT
.sp 1P
.LP
10.4.2.1\ \ A complete message is composed of message elements. Each
element contains an element identifier, a data field and an indication of
element length (explicit or implicit).
.sp 9p
.RT
.sp 1P
.LP
10.4.2.2
\fITransmit a standardized function\fR
.sp 9p
.RT
.PP
Codes for functions may be different from the character sequences, sent
by the user.
.RT
.sp 1P
.LP
10.4.2.3
\fITransmit a service message\fR
.sp 9p
.RT
.PP
A service message is a frame that is transmitted to the subscriber, without
erasing the screen, moving the active position of the cursor, or
changing the contents of the previous display.
.RT
.sp 1P
.LP
10.4.2.4
\fITransmit a service message code\fR
.sp 9p
.RT
.PP
The proper service message is generated by the receiving system and transmitted
to the subscriber.
.RT
.sp 1P
.LP
10.4.2.5
\fITransmit a frame\fR
.sp 9p
.RT
.PP
Billing and other additional information is to be transmitted
together with the frame.
.RT
.sp 1P
.LP
10.4.2.6
\fITransmit data block\fR
.sp 9p
.RT
.PP
By data is meant all types of data that are not listed under
separate items, e.g.\ software. It is necessary to transmit block length when
transmitting transparent data.
.bp
.RT
.sp 1P
.LP
10.4.2.7
\fITransmit field description\fR
.sp 9p
.RT
.PP
A field description is a list of positions on the screen, where an application
program expects additional information to be filled in, either by the user
or by the application program itself. It includes also format and type
of information which allows simple syntax control in the host computer.
.PP
Three formats are recognized; strings, which means any combination of graphical
characters including space, integers\ (0\(hy9), and free
format.
.PP
A field may be of input and/or output type. An input field is a field where
the information is user originated. An output field is a field in which
the information is filled in by the application program.
.RT
.sp 1P
.LP
10.4.2.8
\fITransmit a user message to an application\fR
.sp 9p
.RT
.PP
A user message is the data that is filled in by the user according to a
field description. It is sent to the external computer. The transmission
is initiated either by a send\(hyfunction if it is available, or when all
input
fields are filled. The use of a delimiter causes the rest of the field to be
filled with spaces. If a delimiter is used in the first position of a combined
input and output field, the contents remain unchanged.
.RT
.sp 1P
.LP
10.4.2.9
\fITransmit an application message\fR
.sp 9p
.RT
.PP
An application message is a block of data to be filled into the
output fields, defined by a field description. It may be sent either in the
same message as the field description, or after.
.RT
.sp 1P
.LP
10.4.2.10
\fIRequest information on terminal capability\fR
.sp 9p
.RT
.PP
(For further study.)
.RT
.sp 1P
.LP
10.4.2.11
\fITransmit information on terminal capability\fR
.sp 9p
.RT
.PP
(For further study.)
.RT
.sp 1P
.LP
10.4.2.12
\fIError condition element\fR
.sp 9p
.RT
.PP
The detection of contradicting information in a system will result in an
error condition message to the other system, e.g.\ data with a format
different to the corresponding field description. The entire message causing
the error will be ignored, and it is the responsibility of its transmitting
system to handle the error properly.
.RT
.sp 2P
.LP
10.5
\fIUser to data base protocol\fR
.sp 1P
.RT
.PP
10.5.1
In order to use Videotex service, a user must be able to
generate a set of functions which enables him to access and use different
applications. A set of user functions is listed in Recommendation\ F.300.
.sp 9p
.RT
.PP
10.5.2
The minimum set of characters to code these functions contains the digits\
0\(hy9 and two other symbols. For some applications however, the generation
of alphanumeric as well as pictorial and attribute information and other
control characters may be needed.
.PP
10.5.3
Although it is desirable that all Videotex services employ the
same keying sequences and visual identifiers for these functions, there are
historical reasons why there will be different manners of coding the same
user functions.
.PP
10.5.4
Accessing the national service of another country using an
international connection between services is possible, if the user obeys the
function coding rules of the service of the other country. It is, however,
possible that the local data bank may be able to translate the local keying
sequence into the appropriate command in a national service level
(see \(sc\ 10.4.2.4). This subject is left for further study.
.bp
.sp 2P
.LP
\fB11\fR \fBInterworking with other services\fR
.sp 1P
.RT
.sp 1P
.LP
11.1
\fITelex\(hyVideotex\fR
.sp 9p
.RT
.PP
11.1.1
Telex is a message transfer service and therefore, interworking between
telex and Videotex should be limited to the exchange of alphanumeric
text between terminal equipments.
.sp 9p
.RT
.PP
11.1.2
Only the graphic characters of the Videotex graphic character
repertoire corresponding to International Telegraph Alphabet No.\ 2 should be
used to compose messages.
.PP
11.1.3
The message format will be limited by the Videotex page format.
.PP
11.1.4
Telex can only display alphanumeric information without the
capability of displaying the other attributes of Videotex.
.sp 2P
.LP
11.2
\fITeletex\(hyVideotex\fR
.sp 1P
.RT
.sp 1P
.LP
11.2.1
\fIGraphic character repertoire\fR
.sp 9p
.RT
.sp 1P
.LP
11.2.1.1\ \ The Teletex and Videotex graphic repertoires are largely
identical. The following fallback representations of Videotex characters
(see Table\ 2/T.100), may be transcoded at a Videotex\(hyTeletex interworking
facility.
.sp 9p
.RT
.ce
\fBH.T. [T3.100]\fR
.ce
TABLE\ 2/T.100
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(60p) | cw(60p) .
Identifier Videotex character Fallback representation
_
.T&
cw(42p) | cw(60p) | cw(30p) | cw(30p) .
SM30 \(<- < SA03
.T&
cw(42p) | cw(60p) | cw(30p) | cw(30p) .
SM31 \(ra > SA05
.T&
cw(42p) | cw(60p) | cw(30p) | cw(30p) .
SM32 \(ua ! SP03
.T&
cw(42p) | cw(60p) | cw(30p) | cw(30p) .
SM33 \(da ! SP02
.T&
cw(42p) | cw(60p) | cw(30p) | cw(30p) .
SP19 ` ` SP05
.T&
cw(42p) | cw(60p) | cw(30p) | cw(30p) .
SP20 ' ` SP05
.T&
cw(42p) | cw(60p) | cw(30p) | cw(30p) .
SP21 \*Q " SP04
.T&
cw(42p) | cw(60p) | cw(30p) | cw(30p) .
SP22 \*U " SP04
.T&
cw(42p) | cw(60p) | cw(30p) | cw(30p) .
SM12 \(em \(em \(em SP10
.T&
cw(42p) | cw(60p) | cw(30p) | cw(30p) .
MG01 to MG63 Block graphics / SP12
_
.TE
.nr PS 9
.RT
.ad r
\fBTable 2/T.100 [T3.100], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
11.2.1.2\ \ For Teletex terminals having the ability to present the
Videotex character repertoire in its entirety, the need for this transcoding
disappears. Therefore, on initial call establishment, a determination of the
terminal display/printing capabilities must be made by handshaking.
.sp 9p
.RT
.sp 2P
.LP
11.2.2
\fIControl functions\fR
.sp 1P
.RT
.sp 1P
.LP
11.2.2.1\ \ Transcoding of the Videotex attribute control functions is for
further study.
.sp 9p
.RT
.sp 2P
.LP
11.2.3
\fIFormat\fR
.sp 1P
.RT
.sp 1P
.LP
11.2.3.1\ \ Interworking between Videotex and Teletex will be limited to
the Videotex display frame format.
.sp 9p
.RT
.sp 1P
.LP
11.3
\fIVideotex\(hyfacsimile\fR
.sp 9p
.RT
.PP
(For further study.)
.RT
.sp 1P
.LP
11.4
\fIVideotex\(hyTeletex\fR
.sp 9p
.RT
.PP
(For further study.)
.bp
.RT
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation T.100)
.sp 9p
.RT
.ce 0
.ce 1000
\fBPart of the code extension scheme of ISO 2022\fR
.sp 1P
.RT
.ce 0
.LP
.rs
.sp 47P
.ad r
\fBFigure Annex A, p.
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce 1000
ANNEX\ B
.ce 0
.ce 1000
(to Recommendation T.100)
.sp 9p
.RT
.ce 0
.ce 1000
\fBRepertoire of graphic characters\fR \v'1P'
.sp 1P
.RT
.ce 0
.LP
B.1
\fIGeneral\fR
.sp 1P
.RT
.PP
B.1.1
This annex defines the basic graphic repertoire of the
international Videotex service
. This repertoire consists of the total range of non\(hypictorial symbols,
which may be communicated between Videotex
services and terminals by means of coded character sets for Latin\(hyalphabet
based languages.
.sp 9p
.RT
.PP
B.1.2
The repertoire of graphic characters defined in this part of the Recommendation
consists of:
.sp 9p
.RT
.LP
a)
Latin alphabetic characters, listed in \(sc\ B.2, which
comprise:
.LP
\(em
the 52 small and capital letters of the basic Latin
alphabet,
.LP
\(em
combinations of basic Latin letters and diacritical marks,
.LP
\(em
special alphabetic characters, which are neither
basic Latin letters nor combinations of basic Latin
letters and diacritical marks,
.LP
b)
non\(hyalphabetic characters, listed in \(sc\ B.3, which comprise decimal
digits, currency signs, punctuation marks, arithmetic signs
and miscellaneous symbols that have individual special meanings.
.PP
B.1.3
A diacritical mark has no meaning as an individual character but is used
only in combination with a basic Latin letter to form an accented letter
or an umlaut.
.sp 9p
.RT
.PP
B.1.4
The repertoire of graphic characters defined in this part of the Recommendation
contains a limited set of accented letters and umlauts.
.sp 9p
.RT
.sp 2P
.LP
B.2
\fILatin alphabetic characters\fR
.sp 1P
.RT
.PP
B.2.1
The repertoire of Latin alphabetic characters is identical to that specified
in \(sc\ 3.2.2 of Recommendation\ T.61 (for the Teletex basic
repertoire of graphic characters).
.sp 9p
.RT
.sp 2P
.LP
B.3
\fINon\(hyalphabetic characters\fR
.sp 1P
.RT
.PP
B.3.1
Decimal digits (0 to 9), currency signs, arithmetic signs,
subscripts and superscripts and fractions are as specified in \(sc\(sc\
3.2.3.1,
3.2.3.2, 3.2.3.4, 3.2.3.5 and\ 3.2.3.6 of Recommendation\ T.61.
.sp 9p
.RT
.PP
B.3.2
Punctuation marks are as specified in \(sc\ 3.2.3.3 of
Recommendation\ T.61, with the exclusion of\ SP09 (low line) and the addition
of\ SP19 to\ SP22, which are as shown in Table\ B\(hy1/T.100.
.sp 9p
.RT
.PP
B.3.3
Miscellaneous symbols are as shown in Table B\(hy2/T.100.
.sp 9p
.RT
.PP
B.3.4
The lists in Tables\ B\(hy1/T.100 and B\(hy2/T.100 are composed as described
in the following.
.sp 9p
.RT
.PP
The first column contains the identifier of each character,
assigned in accordance with the identification system explained in Annex\
C of Recommendation\ T.61.
.PP
The second column presents the graphical representation of the
character.
.PP
The third column specifies the name or the description of the
character.
.bp
.RT
.ce
\fBH.T. [T4.100]\fR
.ce
TABLE\ B\(hy1/T.100
.ce
\fBPunctuation marks\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(60p) | cw(60p) | cw(60p) .
Identifier Graphic Name or description
_
.T&
cw(60p) | cw(60p) | lw(60p) .
SP19 ` Single quotation mark left
.T&
cw(60p) | cw(60p) | lw(60p) .
SP20 ' Single quotation mark right
.T&
cw(60p) | cw(60p) | lw(60p) .
SP21 \*Q Double quotation mark left
.T&
cw(60p) | cw(60p) | lw(60p) .
SP22 \*U Double quotation mark right
.TE
.LP
\fINote\fR
\ \(em\ In Videotex (and Teletex), \fIquotation mark, apostrophe\fR
| nd
\fIcomma\fR
| re independent characters that cannot have the meaning of
diacritical marks.
.nr PS 9
.RT
.ad r
\fBTable B\(hy1/T.100 [T4.100], p.
.sp 1P
.RT
.ad b
.RT
.ce
\fBH.T. [T5.100]\fR
.ce
TABLE\ B\(hy2/T.100
.ce
\fBMiscellaneous symbols\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(60p) | cw(90p) .
Identifier Graphic Name or description
_
.T&
cw(48p) | cw(60p) | lw(90p) .
SM01 ## Number sign
.T&
cw(48p) | cw(60p) | lw(90p) .
SM02 % Percent sign
.T&
cw(48p) | cw(60p) | lw(90p) .
SM03 & Ampersand
.T&
cw(48p) | cw(60p) | lw(90p) .
SM04 * Asterisk
.T&
cw(48p) | cw(60p) | lw(90p) .
SM05 \ Commercial at
.T&
cw(48p) | cw(60p) | lw(90p) .
SM12 \(em Horizontal bar
.T&
cw(48p) | cw(60p) | lw(90p) .
SM13 | Vertical line
.T&
cw(48p) | cw(60p) | lw(90p) .
SM17 \(*m Micro sign
.T&
cw(48p) | cw(60p) | lw(90p) .
SM18 \(*W Ohm sign
.T&
cw(48p) | cw(60p) | lw(90p) .
SM19 \uo\d Degree sign
.T&
cw(48p) | cw(60p) | lw(90p) .
SM20 o Ordinal indicator, masculine
.T&
cw(48p) | cw(60p) | lw(90p) .
SM21 a Ordinal indicator, feminine
.T&
cw(48p) | cw(60p) | lw(90p) .
SM24 \(sc Section sign
.T&
cw(48p) | cw(60p) | lw(90p) .
SM25 \ Paragraph sign, pilcrow
.T&
cw(48p) | cw(60p) | lw(90p) .
SM26 \fB.\fR Middle dot
.T&
cw(48p) | cw(60p) | lw(90p) .
SM30 \(<- Leftward arrow
.T&
cw(48p) | cw(60p) | lw(90p) .
SM31 \(ra Rightward arrow
.T&
cw(48p) | cw(60p) | lw(90p) .
SM32 \(ua Upward arrow
.T&
cw(48p) | cw(60p) | lw(90p) .
SM33 \(da Downward arrow
_
.TE
.nr PS 9
.RT
.ad r
\fBTable B\(hy2/T.100 [T5.100], p.
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fBRecommendation\ T.101\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBINTERNATIONAL\ INTERWORKING\ FOR\ VIDEOTEX\ SERVICES\fR
.EF '% Fascicle\ VII.5\ \(em\ Rec.\ T.101''
.OF '''Fascicle\ VII.5\ \(em\ Rec.\ T.101 %'
.ce 0
.sp 1P
.ce 1000
\fI(Malaga\(hyTorremolinos, 1984; amended at Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.ce 1000
CONTENTS
.ce 0
.sp 1P
.LP
Preamble
.sp 1P
.RT
.sp 1P
.LP
1
Purpose and scope of the Recommendation
.sp 9p
.RT
.LP
2
Interworking between Videotex services \(em General
.LP
3
International interworking of Videotex service
.LP
4
International interworking between gateways
.LP
5
International interworking between a terminal and a host
.LP
6
Content architecture class attributes
.LP
7
Content portion attributes
.LP
8
Formal definition of Videotex dependent data type
.LP
\fINote\fR \ \(em\ Annexes B, C and D will not be published in Fascicle\
VII.5 (T\(hySeries Recommendations) but will be issued as a separate publication.
.FE
\fIAnnex\ A\fR \(em
Interworking data syntax (IDS) described in ASN.1
(Recommendation\ X.208)
.LP
\fIAnnex\ B\fR \(em
Data syntax I
.LP
\fIAnnex\ C\fR \(em
Data syntax II
.LP
\fIAnnex\ D\fR \(em
Data syntax III
.LP
\fBPreamble\fR
.sp 1P
.RT
.sp 2P
.LP
The CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR
.sp 9p
.RT
.PP
(a)
that Videotex services have been implemented in
different countries/regions using different data syntaxes referred to as
data syntax\ I, data syntax\ II and data syntax\ III, which have an equal
status;
.PP
(b)
that the CCIR is studying standards for broadcast
Teletext services for general reception and has expressed a view that it
is desirable that terminal equipment compatibility should exist between
broadcast Teletext systems for general reception and public network\(hybased
data base systems;
.PP
(c)
that different countries/regions are entitled to use their existing systems;
.PP
(d)
that interworking between Videotex services in
different countries may require transcoding and/or conversion;
.PP
(e)
that the interworking between Videotex services may be provided by using
different types of networks such as the public switched
telephone network (PSTN), packet switched public data network (PSPDN),
circuit switched public data network (CSPDN), integrated services digital
network
(ISDN),\ etc.;
.PP
(
f
)
that Videotex interworking protocols
should offer a large degree of compatibility with protocols used in other
telematic services,
.sp 1P
.LP
\fIrecommends\fR
.sp 9p
.RT
.PP
that the following technical provisions be applied for
international interworking for Videotex services.
.bp
.sp 2P
.LP
\fB1\fR \fBPurpose and scope of the Recommendation\fR
.sp 1P
.RT
.sp 1P
.LP
1.1
\fIPurpose\fR
.sp 9p
.RT
.PP
The purpose of this Recommendation is:
.RT
.LP
a)
to facilitate the interworking of different Videotex
services;
.LP
b)
to identify parameters needed to communicate with Videotex terminals;
.LP
c)
to provide technical recommendations desirable for potential interworking
of other telematic services with Videotex services.
.sp 2P
.LP
1.2
\fIScope\fR
.sp 1P
.RT
.PP
1.2.1
This Recommendation describes the characteristics of coded
information that is exchanged between countries participating in the
international interactive Videotex service.
.sp 9p
.RT
.PP
1.2.2
Videotex systems are text communication systems having in
addition the capability of a given level of pictorial representation and a
repertoire of display attributes. The text and the pictures obtained are
intended to be displayed using the current television\ (TV) raster standards
of the different countries.
.PP
1.2.3
Different data syntaxes are offered as a choice for the
Administrations to implement their national services. Substantial degrees of
compatibility exist between these options, but some transcoding and/or
conversion may be necessary to facilitate interworking.
.PP
1.2.4
For the purpose of the international service, different data
syntaxes have been identified:
.LP
a)
interworking data syntax;
.LP
b)
data syntax I;
.LP
c)
data syntax II;
.LP
d)
data syntax III;
.LP
e)
other syntaxes are for further study.
.sp 2P
.LP
\fB2\fR \fBInterworking between Videotex services \(em General\fR
.sp 1P
.RT
.PP
2.1
It is the possibility of Administrations to decide in which
network(s) the Videotex service(s) are to be provided.
.sp 9p
.RT
.PP
2.2
Serveral possibilities are considered below:
.sp 9p
.RT
.PP
2.2.1
Videotex service operated on the PSTN; the communication between a Videotex
terminal and a Videotex host computer is established over the PSTN.
.PP
2.2.2
Videotex service operated on the PSTN and a public data network
(PDN) (generally a PSPDN); the communication between a Videotex terminal
connected to the PSTN and a Videotex host computer connected to a PDN is
established via a Videotex access prior or a Videotex service center
interfacing between both networks.
.PP
2.2.3
Other possibilities (CSPDN, ISDN, etc.) could also be considered.
.PP
2.3
International interworking between Videotex services via gateways and connected
to any network (PSTN, PSPDN, CSPDN, ISDN,\ etc.) may be possible. Such
interworking allows a Videotex terminal pertaining to a Videotex service
to access a Videotex host computer pertaining to another Videotex service.
International interworking between Videotex terminal in one country and a
Videotex host in another country may also be possible. All international
data exchange should comply with the specifications contained in this
Recommendation. (See Recommendation\ F.300 for the service description).
.sp 2P
.LP
\fB3\fR \fBInternational interworking of Videotex service\fR
.sp 1P
.RT
.PP
3.1
Videotex interworking allows a Videotex terminal in a given
country to interact in real time with Videotex application located in a
different country.
.sp 9p
.RT
.PP
3.2
International interworking between Videotex services should use
those functions that are defined in the data syntaxes implemented by the
Administrations concerned: data syntaxes\ I, II and\ III defined in Annexes.
.bp
.sp 1P
.LP
3.3
\fIInternational interworking configurations\fR
.sp 9p
.RT
.PP
The various configurations for international interworking are
defined in Recommendation\ F.300. The two major classes of interworking are
defined below.
.RT
.sp 1P
.LP
3.3.1
\fIGateway to gateway interworking\fR
.sp 9p
.RT
.PP
This class of interworking involves communication between gateways located
in each country and where all the data handling processes involved by the
interworking are performed. The protocols and data syntaxes for this class
of interworking are specified in \(sc\ 4.
.RT
.sp 1P
.LP
3.3.2
\fITerminal to host interworking\fR
.sp 9p
.RT
.PP
This class of interworking involves communication between a
terminal and a host located in different countries, either directly or
through a conversion unit situated in the country where the terminal is
located.
Several cases have been identified. The protocols and data syntaxes for the
various cases of this class of interworking are specified in \(sc\ 5.
.RT
.sp 2P
.LP
\fB4\fR \fBInternational interworking between gateways\fR
.sp 1P
.RT
.PP
The international interworking between gateways allows a Videotex terminal
located in country\ A to access the Videotex services located in
country\ B via a Videotex service of country\ A. The configuration for the
international interworking between gateways is described by
Figure\ 1/T.101:
.RT
.LP
.rs
.sp 8P
.ad r
\fBFigure 1/T.101 TO803410\(hy89, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
4.1
\fIInternational interworking at network level\fR
.sp 1P
.RT
.PP
4.1.1
International interworking between Videotex services should
preferably take place between networks of the same type when these networks
are provided by both Administrations involved (PSPDN, CSPDN, ISDN and leased
lines).
.sp 9p
.RT
.PP
4.1.2
The network service definition of open systems interconnection for CCITT
application is defined in Recommendation\ X.213.
.PP
4.1.3
When the interworking takes place between Videotex services
operated on different types of network, Recommendation\ X.75 should apply.
Interworking with ISDN should be in accordance with Recommendation\ T.90.
.sp 1P
.LP
4.2
\fITransport layer\fR
.sp 9p
.RT
.PP
The transport layer service of open systems interconnection for
CCITT applications is defined in Recommendation\ X.214.
.PP
The transport protocol of open systems interconnection for CCITT
applications is specified in Recommendation\ X.224.
.PP
Both classes 0 (corresponding to Recommendation T.70) and 2 may be
used.
.PP
When class 0 is selected, then the protocol used is fully compatible with
CCITT Recommendation\ T.70. When class\ 2 is selected, explicit flow control
is to be used.
.bp
.RT
.sp 1P
.LP
4.3
\fISession layer\fR
.sp 9p
.RT
.PP
This session layer service of open systems interconnection for
CCITT applications is defined in Recommendation\ X.215. The session protocol
of open systems interconnection for CCITT applications is specified in
Recommendation\ X.225.
.PP
The use of the session protocols by Videotex interworking is defined in
Recommendation\ T.523.
.RT
.sp 2P
.LP
4.4
\fIPresentation layer\fR
.sp 1P
.RT
.sp 1P
.LP
4.4.1
\fIPresentation protocol\fR
.sp 9p
.RT
.PP
The presentation layer service of open systems interconnection for CCITT
applications is defined in Recommendation\ X.216. Presentation protocol
of open systems interconnection for CCITT applications is specified in
Recommendation\ X.226.
.PP
The use of the presentation protocols by Videotex interworking is
defined in Recommendation\ T.523.
.RT
.sp 1P
.LP
4.4.2
\fICoding of Videotex information\fR
.sp 9p
.RT
.LP
\fICoding of the contents of the display\(hydata element\fR
.PP
The Videotex content conforms to one of the several different data syntaxes.
A data syntax, referred to as
interworking data syntax
, is
described in Annex\ A. There are three existing data syntaxes, based on
Recommendation\ T.50 and referred to as data syntax\ I, data syntax\ II
and data syntax\ III. They are described in Annex\ B, Annex\ C and Annex\
D respectively.
All the four annexes form an integral part of this Recommendation.
.PP
Different Administrations implementing a Videotex service may use one of
the three above data syntaxes.
.PP
If two countries implement the same data syntax, then Videotex
interworking between the two countries can use that same data syntax.
.PP
If one country implements one data syntax and another country
implements a different data syntax, then Videotex interworking between
the two countries can either:
.RT
.LP
i)
use the interworking data syntax as the intermediary syntax. Transcoding/conversion
into and from the interworking data
syntax by the two countries will be required; or
.LP
ii)
use one of the two data syntaxes with
transcoding/conversion performed either at the originating
or at the destination country.
.PP
For identification of the particular in\(hyuse data syntax (I or II or
III), the designation and invocation of the \*Qcomplete code\*U escape
sequence may be used:
.LP
ESC 2/5 4/3 for data syntax I
.LP
ESC 2/5 4/4 for data syntax II
.LP
ESC 2/5 4/1 for data syntax III
.PP
The \*Qcomplete code\*U environment will be terminated either by the sequence:
.LP
ESC 2/5 4/0
.LP
or by the designation and invocation of any other complete code.
.sp 1P
.LP
4.5
\fIApplication layer\fR
.sp 9p
.RT
.PP
The association control service element (ACSE) of open systems
interconnection for CCITT applications is defined in Recommendation\ X.217.
The association control service element (ACSE) protocol of open systems
interconnection for CCITT applications is specified in Recommendation\ X.227.
.PP
The application layer for Videotex interworking makes use of the
following Recommendations:
.RT
.LP
\(em
Recommendation T.400: Introduction to document architecture, transfer
and manipulation
.LP
\(em
Recommendation T.411: Open document architecture (ODA) and
interchange format; Introduction and general principles
.LP
\(em
Recommendation T.412: Open document architecture (ODA) and
interchange format; Document structures
.LP
\(em
Recommendation T.414: Open document architecture (ODA)
and interchange format; Document profile
.LP
\(em
Recommendation T.415: Open document architecture (ODA) and
and interchange format; Document interchange format (ODIF).
.bp
.PP
The application layer for Videotex interworking makes use of DTAM (document
transfer and manipulation) service and protocol described in
Recommendations\ T.431, T.432 and\ T.433.
.PP
The application layer for Videotex interworking makes use of
operational structures described in Recommendation\ T.441.
.PP
Recommendation T.564 describes the Videotex interworking application profile
and the gateway characteristics.
.PP
Recommendation T.504 describes the document application profile for
Videotex interworking.
.PP
Recommendation T.523 describes the communication application profile for
Videotex interworking.
.PP
Recommendation T.541 describes the operational application profile for
Videotex interworking.
.RT
.sp 1P
.LP
4.6
\fIRelation with DTAM/ODA\fR
.sp 9p
.RT
.PP
The relations with the document architecture (Recommendation T.412) and
the document interchange format (see Recommendation\ T.415) are expressed
through the content architecture class attributes, and the content portion
attributes are described in \(sc\(sc\ 6 and\ 7.
.RT
.sp 2P
.LP
\fB5\fR \fBInternational interworking between a terminal and a host\fR
.sp 1P
.RT
.sp 1P
.LP
5.1
\fIAccess via PSTN or ISDN bearer service\fR
.sp 9p
.RT
.LP
.rs
.sp 4P
.ad r
\fBFigure T.101 TO803420\(hy89, p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
The protocols to be used in the ISDN Videotex teleservice are for
further study.
.FE
In this configuration, the terminal uses the international PSTN
(respectively the ISDN bearer services) to reach the host. On the international
link, the following protocols should be used:
.RT
.LP
layers 1 to 3 via PSTN:
the protocols defined by the host;
.LP
layers 1 to 3 via ISDN bearer service
:
Recommendation\ T.90;
.LP
layers 4 to 7:
the protocols (if any) defined by the host
located in country\ B;
.LP
data syntax:
data syntax defined by the host;
.LP
dialogue/service functions:
functions defined by the
host.
.sp 1P
.LP
5.2
\fIAccess via PSPDN or ISDN bearer service\fR
.sp 9p
.RT
.LP
.rs
.sp 4P
.ad r
\fBFigure T.101 TO803430\(hy89, p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
In this configuration, the terminal uses the international PSPDN
(respectively the ISDN bearer services) to reach the host. On the international
link, the following protocols should be used:
.RT
.LP
layers 1 to 3 via PSPDN:
Recommendation X.75;
.LP
layers 1 to 3 via ISDN bearer service
:
Recommendation\ T.90;
.LP
layers 4 to 7:
the protocols (if any) defined by the host
located in country\ B;
.LP
data syntax:
data syntax defined by the host;
.LP
dialogue/service functions:
functions defined by the
host.
.bp
.sp 1P
.LP
5.3
\fIAccess via PSPDN/PAD\fR
.sp 9p
.RT
.LP
.rs
.sp 7P
.ad r
\fBFigure T.101 TO803440\(hy89, p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
In this configuration, the terminal is connected to a PAD which
gives access to the international PSPDN; both terminal and PAD are located
in country\ A. The type of connection between the terminal and the PAD
is a
national matter (generally the PSTN or a leased line).
.PP
The host of country B may be accessed through the international PSPDN.
The type of connection between the host and the national PSPDN is a national
matter (generally a leased line).
.PP
On the international link, the following protocols should be
used:
.RT
.LP
layers (1 to 3):
Recommendation X.75;
.LP
above layer 3:
Recommendation X.29 + Recommendation X.3;
.LP
data syntax:
data syntax defined by the host located in country B;
.LP
dialogue/service functions:
functions defined by the host.
.sp 1P
.LP
5.4
\fIAccess via PSPDN through a VIU\fR
.sp 9p
.RT
.LP
.rs
.sp 7P
.ad r
\fBFigure T.101 TO803450\(hy89, p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
In this configuration, the terminal is connected to a VIU
(Videotex interface unit) which gives access to the international PSPDN;
both the terminal and the VIU are located in country\ A. The type of connection
between the terminal and the VIU is a national matter (generally the PSTN
or a leased line). The VIU performs two functions: it supports terminals
and
converts data syntaxes. It is up to the Administration of country\ A to
decide how a VIU is implemented: it may be realized as a separate system
or integrated with an existing equipment (PAD or Videotex access point
for example).
.PP
The host country B may be accessed through the international PSPDN.
The type of connection between the host and the national PSPDN is a national
matter (generally a leased line).
.PP
On the international link, the following protocols should be
used
:
.RT
.LP
layers (1 to 3):
Recommendation X.75;
.LP
above layer 3:
Recommendation X.29 + Recommendation X.3.
Alternatively Recommendation\ X.200 based protocols can be
used. For this case, application profiles will
need to be defined in T.500
Series of Recommendation. This is for further
study.
.LP
data syntax:
the data syntax defined by the host located in
country\ B;
.LP
dialogue/service functions:
those defined by the host.
.bp
.sp 1P
.LP
5.5
\fIAccess via PSPDN through a VSU\fR
.sp 9p
.RT
.LP
.rs
.sp 10P
.ad r
\fBFigure T0803460\(hy89, p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
In this configuration, the terminal is connected to a VSU
(Videotex service unit) which gives access to the international PSPDN; both
the terminal and the VSU are located in country\ A. A VSU is a VIU which
is also in charge of handling application charge and accounting. It is
up to
Administration of country\ A to decide to set up or not a VSU and to decide
how a VSU, if any, is to be implemented: it may be realized as a separate
system or integrated with an existing equipment (PAD, Videotex access point
or Videotex service center).
.PP
The host in country B may be reached through the international PSPDN. The
type of connection between the host and the national PSPDN is a national
matter (generally a leased line).
.PP
On the international link, the following protocols should be
used:
.RT
.LP
layers (1 to 3):
Recommendation X.75,
.LP
above layer 3:
Recommendation X.200 based protocols.
.LP
For this case applications profiles need to be
defined in the T.500 Series. This is for further
study.
.LP
Alternatively Recommendation X.29 plus Recommendation X.3 may be used.
Extensions (Application rules) to Recommendation\ X.29 are necessary
(see \(sc\ 5.6);
.LP
data syntax:
the data syntax defined by the host located in
country\ B;
.LP
dialogue/service functions:
those defined by the host.
.sp 1P
.LP
5.6
\fIApplication rules for X.29 to support administrative functions\fR
.sp 9p
.RT
.PP
When an international communication is established via a VSU using Recommendation\
X.29, X.29 Videotex commands may be used to allow application
charges (if any) to be passed from the host to the VSU.
.PP
Videotex commands should be sent in complete packet sequences with the
Q\ bit set to one.
.PP
Videotex commands use a T(ype)\(hyL(ength)\(hyV(alue) encoding. Fixed length
commands do not require any length indicator. When used, length indicator
is
coded on two bytes and defines the total length in bytes of the
V\ field.
.PP
In order to distinguish Videotex commands from PAD commands as
currently defined by Recommendation\ X.29, the type value of a Videotex
command is defined with the most significant bit set to one.
.PP
The following values are proposed to support the exchange of charging of
international connections:
.RT
.LP
\(em
Administration
(99H) L2 charging (82H), L2
charging\(hyparameter.
.LP
The charging parameter may take either the value service\(hyoperation
(80H) or the value application\(hyoperation (81H); both values may be present
within the same charging parameter:
.LP
\(em
service\(hyoperation
(80H)\ L1\ service\(hyparameter
.LP
\(em
application\(hyoperation
(81H)\ L1 application
parameter.
.bp
.PP
The service parameter is time dependent and may correspond either to the
amount period (80H) or to the duration of the period (81H) or to a
combination of them:
.LP
\(em
amount
(80H)\ L1 value
.LP
\(em
period
(81H)\ L1 value.
.PP
The application parameter may be frame dependent (80H), time
dependent (81H) or transaction dependent (82H) or a combination of them:
.LP
\(em
frame
(80H)\ L1 value
.LP
\(em
time
(81H)\ L1 charging\(hyon\(hytime\(hyparameter
.LP
\(em
transaction
(82H)\ L1 value.
.PP
The charging\(hyon\(hytime parameter is organized as the service
parameter.
.LP
L1 is an acronym for a length coded on one byte.
.LP
L2 is an acronym for a length indicator coded on two bytes.
.PP
The following depicts the coding mechanism:
.LP
.sp 2
.ce
\fBH.T. [T1.101]\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(210p) .
{
Administration L2 Charging L2 (Service) (Application)
.line
(99H)
(82H)
}
.T&
lw(210p) .
{
(Service) ::= Service L1 (Amount L1 value) (Period L1 value)
.line
(80H)
(80H)
(81H)
}
.T&
lw(210p) .
{
(Application) ::= Application L1 (Frame) (Time) (Transaction)
.line
(81H)
}
.T&
lw(210p) .
{
(Frame) ::= Frame L1 value
.line
(80H)
}
.T&
lw(210p) .
{
(Time) ::= Time L1 (Amount L1 value) (Period L1 value)
.line
(81H)
(80H)
(81H)
}
.T&
lw(210p) .
{
(Transaction) ::= Transaction L1 value
.line
(82H)
}
.TE
.nr PS 9
.RT
.ad r
\fBTable 1/T.101 [T1.101], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 7
.sp 2P
.LP
\fB6\fR \fBContent architecture class attributes\fR
.sp 1P
.RT
.sp 1P
.LP
6.1
\fIContent architecture class\fR
.sp 9p
.RT
.PP
The value of the attribute "content architecture class" of a basic component
description that conforms to this Recommendation\ T.101 is a ASN1
object identifier with the value.
.RT
.sp 1P
.ce 1000
{ | \ 1\ 8\ 16\ 3\ }
.ce 0
.sp 1P
.LP
6.2
\fIContent type\fR
.sp 9p
.RT
.PP
The content architecture class attribute "content type" cannot be used
to specify the content architecture class defined in this
Recommendation.
.bp
.RT
.sp 2P
.LP
\fB7\fR \fBContent portion attributes\fR
.sp 1P
.RT
.sp 1P
.LP
7.1
\fIType of coding\fR
.sp 9p
.RT
.LP
Classification
Defaultable
.LP
Applicability
Videotex content architecture class
.LP
Structure
ASN1 object identifier
.LP
Permissible values
ASN1 object identifier
.LP
{ 0\ 1\ 8\ 16\ 4\ }
for \*QIDS encoding\*U
.LP
{ 0\ 1\ 8\ 16\ 5\ }
for \*QData syntax I encoding\*U
.LP
{ 0\ 1\ 8\ 16\ 6\ }
for \*QData syntax II encoding\*U
.LP
{ 0\ 1\ 8\ 16\ 7\ }
for \*QData syntax III encoding\*U
.LP
Default value:
\*QIDS encoding\*U
.LP
Definition:
for Videotex interworking, the possible values
correspond to the data syntaxes described in Annexes\ A, B, C, D of this
Recommendation.
.sp 1P
.LP
7.2
\fISpecific coding attributes\fR
.sp 9p
.RT
.PP
These attributes provide additional information required for
encoding/decoding the content information, as well as other information
intrinsic to the content portion and type of coding.
.RT
.sp 1P
.LP
7.2.1
\fISubset\fR
.sp 9p
.RT
.LP
Classification
Defaultable
.LP
Applicability
Videotex content architecture class
.LP
Type of coding \*QIDS encoding\*U
.LP
Values
Integer [0, 1 to 5, 81 to 92]
.LP
Default value
0
.LP
Definition
This attribute identifies the subset (rank or
profile) used within the IDS. Value\ 0 is used when no
subset is specified.
.sp 1P
.LP
7.2.2
\fIRank\fR
.sp 9p
.RT
.LP
Classification
Defaultable
.LP
Applicability
Videotex content architecture class
.LP
Type of coding \*QData syntax\ I encoding\*U
.LP
Values
Integer\ [0, 1 to 5]
.LP
Default value
0
.LP
Definition
This attribute identifies the rank used within Data syntax\ I. Value\
0 is used when the rank is not specified.
.sp 1P
.LP
7.2.3
\fIProfile\fR
.sp 9p
.RT
.LP
Classification
Defaultable
.LP
Applicability
Videotex content architecture class
.LP
Type of encoding \*QData Syntax\ II encoding\*U
.LP
Values
Integer\ [0, 81 to 92]
.LP
Default value
0
.LP
Definition
This attribute identifies the profile used within Data Syntex\ II. Value\
0 is used when the profile is not specified.
.sp 2P
.LP
\fB8\fR \fBFormal definition of \fR \fBVideotex dependent data type\fR
.sp 1P
.RT
.sp 1P
.LP
8.1
\fIIntroduction\fR
.sp 9p
.RT
.PP
This section contains formal definition in ASN.1 notation (defined in Recommendation\
X.208) of the data type corresponding to attributes
applicable to Videotex.
.PP
This data type is:
.RT
.LP
\(em
the data type to represent specific coding attributes.
.bp
.sp 1P
.LP
8.2
\fIRepresentation of specific coding attributes\fR
.sp 9p
.RT
.LP
.sp 5
.ce
\fBH.T. [T2.101]\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(216p) .
.TE
.nr PS 9
.RT
.ad r
\fBTableau [T2.101], p.29\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
8.3
\fISummary of ASN.1 object identifiers\fR | (see Table 1/T.101)
.sp 9p
.RT
.ce
\fBH.T. [T3.101]\fR
.ce
TABLE\ 1/T.101
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(120p) | cw(48p) .
{
Videotex document application profile
} 0\ 1\ 8\ 16\ 0
.T&
lw(120p) | cw(48p) .
{
DM1 communication application profile
} 0\ 1\ 8\ 16\ 1
.T&
lw(120p) | cw(48p) .
{
Videotex operational application profile
} 0\ 1\ 8\ 16\ 2
_
.T&
lw(120p) | cw(48p) .
{
T.101 Content architecture class
} 0\ 1\ 8\ 16\ 3
_
.T&
lw(120p) | cw(48p) .
Type of coding
.T&
lw(120p) | cw(48p) .
\ IDS 0\ 1\ 8\ 16\ 4
.T&
lw(120p) | cw(48p) .
\ Data syntax I 0\ 1\ 8\ 16\ 5
.T&
lw(120p) | cw(48p) .
\ Data syntax II 0\ 1\ 8\ 16\ 6
.T&
lw(120p) | cw(48p) .
\ Data syntax III 0\ 1\ 8\ 16\ 7
_
.T&
lw(120p) | cw(48p) .
Application context 0\ 1\ 8\ 16\ 8
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 1/T.101 [T3.101], p.30\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 30P
.sp 2P
.LP
\fBMONTAGE: ANNEXE A SUR LE RESTE DE CETTE PAGE\fR
.sp 1P
.RT
.LP
.bp