ETSI ETS 300 177 ed.2 (1995-01)

SLOVENSKI STANDARD
01-december-2003
Terminalska oprema (TE) – Videotex – Fotografska skladnja
Terminal Equipment (TE); Videotex; Photographic Syntax
Ta slovenski standard je istoveten z: ETS 300 177 Edition 2
ICS:
33.160.99 Druga avdio, video in Other audio, video and
avdiovizuelna oprema audiovisual equipment
35.180 Terminalska in druga IT Terminal and other
periferna oprema IT peripheral equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN ETS 300 177
TELECOMMUNICATION January 1995
STANDARD Second Edition
Source: ETSI TC-TE Reference: RE/TE-01055
ICS: 33.040.40
Videotex, Photographic Syntax
Key words:
Terminal Equipment (TE);
Videotex;
Photographic Syntax
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
F-06921 Sophia Antipolis CEDEX - FRANCE
Postal address:
650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Office address:
c=fr, a=atlas, p=etsi, s=secretariat - secretariat@etsi.fr
X.400: Internet:
Tel.: +33 92 94 42 00 - Fax: +33 93 65 47 16
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1995. All rights reserved.
New presentation - see History box

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ETS 300 177: January 1995
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.

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ETS 300 177: January 1995
Contents
Foreword .9
1 Scope .11
2 Normative references.11
3 Definitions, symbols and abbreviations.12
3.1 Definitions .12
3.2 Symbols and abbreviations.16
4 Overview .17
5 ISO/IEC 9281, Part 1, syntax and switching structure .17
5.1 Overall switching of coding environment .17
5.2 Switching into the photographic mode.19
5.3 ISO/IEC 9281, Part 1, syntax structure.19
5.3.1 General use of the Length Indicator (LI).20
5.3.2 Use of the Picture Identifier (PI) code .20
6 Coding of the Picture Data Entity (PDE) .21
6.1 Introduction .21
6.2 PDE data content identification mechanism .21
7 Photographic header.23
7.1 Introduction .23
7.2 Header structure .23
7.3 Header functionalities .26
7.3.1 Parameter Status Attribute .26
7.3.1.1 Reset To Default .26
7.3.2 Picture Display Attributes .26
7.3.2.1 Full Screen Display .28
7.3.2.2 Source spect Ratio .28
7.3.2.3 Photo-area LOCation .28
7.3.2.4 Photo-Area Size .28
7.3.2.5 Picture PLacement .29
7.3.2.6 Clear Photo-Area .31
7.3.3 Source Picture Attributes .31
7.3.3.1 Source Picture Comments .31
7.3.3.2 Source Picture Dimensions .33
7.3.3.3 Source PIxel Density .33
7.3.3.4 Source SWeep Direction .34
7.3.3.5 DC Images .34
7.3.4 Source Signal Attributes .35
7.3.4.1 Source Component Description .35
7.3.4.2 Source Component Data Precision .35
7.3.4.3 Source Component Order .36
7.3.4.4 Source Level Assignment .36
7.3.5 Source Coding Algorithm Attributes .37
7.3.5.1 JPEG Coding Mode .37
7.3.5.2 Encoding Table Management .39
7.3.5.3 Application Marker codes Assignment .40
7.3.5.4 T4 Coding Mode .41
7.3.5.5 T6 Coding Mode .41
7.3.6 Transmission Channel Attributes .41
7.3.6.1 Translation Mode Encoding .42

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8 Coding rules. 42
8.1 Purpose. 42
8.2 General rules for coding the header. 42
8.3 Photographic header code assignment. 49
8.3.1 Attribute codes. 49
8.3.2 Parameter codes . 49
8.3.2.1 Parameter Status Attribute. 49
8.3.2.2 Picture display attributes . 49
8.3.2.3 Source picture attributes . 49
8.3.2.4 Source signal attributes. 50
8.3.2.5 Source coding algorithm attributes . 50
8.3.2.6 Transmission channel attributes . 50
8.3.3 Sub-parameter codes . 50
8.4 Encoding of photographic header parameters. 50
8.4.1 Parameter Status Attribute: . 50
8.4.1.1 Reset To Default . 50
8.4.2 Picture Display Attributes . 50
8.4.2.1 Full Screen Display . 50
8.4.2.2 Source ASpect Ratio . 51
8.4.2.3 Photo-area LOCation . 51
8.4.2.4 Photo-Area Size . 51
8.4.2.5 Picture PLacement . 51
8.4.2.6 Clear Photo-Area . 51
8.4.3 Source Picture Attributes . 52
8.4.3.1 Source Picture Comments . 52
8.4.3.2 Source Picture Dimensions . 52
8.4.3.3 Source PIxel Density . 53
8.4.3.4 Source SWeep Direction . 53
8.4.3.5 DC Images . 53
8.4.4 Source Signal Attributes . 54
8.4.4.1 Source Component Description . 54
8.4.4.2 Source Component Data Precision . 54
8.4.4.3 Source Component Order . 54
8.4.4.4 Source Level ASsignment . 54
8.4.5 Source Coding Algorithm Attributes . 55
8.4.5.1 JPEG Coding Mode . 55
8.4.5.2 Encoding Table Management . 55
8.4.5.3 Application Marker codes Assignment . 56
8.4.5.4 T4 Coding Mode . 56
8.4.5.5 T6 Coding Mode . 56
8.4.6 Transmission Channel Attributes . 57
8.4.6.1 Translation Mode Encoding . 57
9 Photographic data. 57
9.1 Introduction. 57
9.2 Translation modes. 57
10 Defaults. 58
10.1 Default values for photographic header attributes . 58
10.1.1 Default parameter status attribute . 58
10.1.2 Default picture display attributes. 58
10.1.3 Default source picture attributes. 58
10.1.4 Default source signal attributes . 59
10.1.5 Default source coding algorithm attributes . 59
10.1.6 Default transmission channel attributes. 60
10.1.7 Default application marker code assignment. 60
10.2 Default tables . 60
10.2.1 Default quantization tables. 60
10.2.1.1 Default quantization tables for CIF images . 60
10.2.1.2 Default quantization tables for 2:1:1 images. 60
10.2.1.3 Default quantization tables for 4:2:2 images. 61
10.2.2 Default Huffman tables . 61
10.2.2.1 Default Huffman table for luminance DC differences . 62

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10.2.2.2 Default Huffman table for chrominance DC differences.62
10.2.2.3 Default Huffman table for luminance AC coefficients.63
10.2.2.4 Default Huffman table for chrominance AC coefficients.66
11 Photographic profiles.69
11.1 Compatible photographic profiles (P1 to P5) .71
11.1.1 Profile P1.71
11.1.2 Profile P2.72
11.1.3 Profile P3.72
11.1.4 Profile P4.73
11.1.5 Profile P5.73
11.2 Private choice of photographic profile (P ) .73
priv
Annex A (informative): Photovideotex tutorial .75
A.1 Introduction.75
A.2 The present state of photovideotex.75
A.3 Image representation .76
A.4 The JPEG compression technique.77
A.4.1 Lossy and lossless compression .77
A.4.2 Modes of encoding.78
A.4.3 The DCT-based coding.79
A.4.3.1 The discrete cosine transform.80
A.4.3.2 Quantization .81
A.4.3.3 Huffman coding [A8].82
A.4.3.3.1 PCM encoding of the DC coefficients.83
A.4.3.3.2 Zigzag Ordering of AC Coefficients .83
A.4.4 Lossless coding .84
A.4.5 Source images and data interleaving.84
A.4.6 Data organisation and signalling parameters .84
A.5 The baseline system .85
A.6 The extended system.85
A.6.1 Coding model for successive approximation .85
A.6.2 Coding model for spectral selection.85
A.6.3 Hierarchical encoding .86
A.7 Summary.86
A.8 Bibliography.86
Annex B (informative): Implementation guidelines on display rendering .87
B.1 Introduction.87
B.2 Rendering of resolution .87
B.2.1 Resolution independence .87
B.2.2 Display rendering guidelines for Data Syntax II profiles .89
B.2.2.1 Pixel alignment .89
B.2.2.1.1 CCIR Recommendation 601, Part 1 4:2:2 resolution .89
B.2.2.1.2 CCIR Recommendation 601, Part 1 2:1:1 resolution .89
B.2.2.1.3 CIF format.89
B.2.2.1.4 QCIF format.89
B.2.2.2 Adjustment of horizontal resolution .90
B.2.2.2.1 "Adding" pixels.90
B.2.2.2.2 "Removing" pixels.90
B.3 The concept of normalised colour space .91

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Annex C (informative): Solutions for common compatible photovideotex databases serving different
resolution terminals. 92
C.1 Introduction. 92
C.2 Hierarchical mode. 92
C.2.1 Coding. 92
C.2.2 Decoding . 94
C.2.3 Example for a "resolution pyramid" for hierarchical build-up. 94
C.2.3.1 Advantages of the suggested technique. 95
C.2.3.1.1 Independence of transmission, decompression and
display . 95
C.2.3.1.2 Independence of image resolution from the terminal
resolution. 95
C.2.3.1.3 Storage gain in the database host through the pyramidal
database . 95
C.2.3.2 Disadvantages . 95
C.3 Special spectral selection . 96
C.3.1 Coding. 96
C.3.2 Decoding . 97
Annex D (informative): Coding examples . 99
D.1 Introduction. 99
D.1.1 Example 1 . 99
D.1.2 Example 2 . 100
D.1.3 Example 3 . 103
D.2 Image positioning examples . 104
D.2.1 Example 1: 640 X 480 picture inside DDA . 104
D.2.2 Example 2: 720 X 576 picture full screen. 105
D.2.3 Example 3: 720 X 346 picture covering upper 60% of full screen . 106
D.3 Example for Source Picture Comments (PCT). 106
D.3.1 An application scenario . 106
D.3.2 Sample logical record of a Source picture: . 107
Annex E (informative): ETSI/ITU-T-CCITT Cross-reference list . 109
Annex F (normative): Encoding parameters values for the 2:1:1. 110
F.1 Introduction. 110
F.2 Encoding parameters for 2:1:1 . 110
F.2.1 Main body of CCIR Recommendation 601, Part 1 . 110
F.2.2 Annex I of the CCIR Recommendation 601, Part 1 . 110
F.2.3 Annex II of the CCIR Recommendation 601, Part 1 . 110
F.2.3.1 Relationship of active line to analogue synchronisation reference . 110
F.2.3.2 Definition of the digital signals Y, C , C , from the primary (analogue)
B R
signals E' , E' and E' . 111
R G B
F.2.4 Annex III of the CCIR Recommendation 601. 111
Annex G (normative): Translation modes . 117
G.1 Mode 0 (No translation, full transparency). 117
G.2 Mode 2 (3-in-4 coding). 117
G.3 Mode 4 (Shift scheme - 7 bits). 118
Annex H (informative): Huffman tables for the "special spectral selection". 119

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H.1 Introduction.119
H.2 Spectral bands .119
H.3 Luminance DC differences.119
H.3.1 List of codelengths.119
H.3.2 List of values.119
H.4 Chrominance DC differences.120
H.4.1 List of codelengths.120
H.4.2 List of values.120
H.5 Luminance AC coefficients.120
H.5.1 List of codelengths.120
H.5.2 List of values.121
H.6 Chrominance AC coefficients.124
H.6.1 List of codelengths.124
H.6.2 List of values.124
Annex J (informative): Examples of local presentation facilities with T4 and T6 encoded data.129
J.1 Local presentation facilities .129
J.2 Local presentation modes .129
J.2.1 Full View Mode .129
J.2.2 Full Width Mode.130
J.2.3 Full Height Mode.130
J.2.4 Original Size Mode.130
J.2.5 Terminal Dependant Mode .131
History.132

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Foreword
This second edition European Telecommunication Standard (ETS) has been prepared by the Terminal
Equipment (TE) Technical Committee of the European Telecommunications Standards Institute (ETSI) in
order to specify a new common data syntax for transmitting photographic images to be used by Videotex
terminal equipment. It is now submitted under the Unified Approval Procedure (UAP) of the ETSI
standards approval procedure.
This ETS is part of a series of ETSs which describe the Videotex presentation layer data syntax.
This ETS defines a data syntax to be used for conveying photographic data in a Videotex environment.
The necessary tools are provided for the transfer of photographic data, typically from a Videotex Host to a
Videotex terminal. This data syntax is equally applicable to either storage or communication applications
and is independent of physical device or transmission media.
This ETS does not deal with the visible appearance of the displayed pictures, however all the necessary
source image information is provided to make the proper physical adaptation at the receiving side. The
specification of post-processing techniques is left to the implementors and is, therefore, outside the scope
of this ETS.
More precisely, this ETS defines the syntax and semantics of image data and image attributes for
photographic Videotex interchange purposes. In particular, it addresses the various aspects of image
dimensionality such as spatial, amplitudinal, temporal and spectral content, it provides some basic tools
for positioning photographic images within a defined area, it also addresses the structure and organisation
of the data and uses standardized compression schemes. In particular, the ISO-Joint Photographic
Experts Group (JPEG) compression algorithm (see ISO/IEC 10918-1 [13]), based on the Discrete Cosine
Transform (DCT), the facsimile ITU-T Recommendation T.4 [17] and CCITT Recommendation T.6 [18]
coding algorithms are used. In this ETS the algorithms or compression techniques themselves are not
described, references are provided.
The intention of this ETS is primarily to provide Videotex application developers with a sufficient set of
photographic transfer tools which are independent of the equipment used to implement/provide them. This
ETS is intended to support operations on and display of, various classes of images from a wide variety of
imaging applications. However, to ensure that compatibility can be achieved between various Videotex
services supporting photographic mode, some realistic and specific characteristics are chosen and
defined in the clause on profiles (clause 11). In the future, other selections might be made allowing the
definition of new recommended profiles.
This ETS closely follows the concepts and coding techniques as described in ISO/IEC 9281-1 [11] for the
identification of pictorial information and for switching between picture environments and coding systems
according to ISO 2022 [10].
Proposed transposition dates
Date of latest announcement of this ETS (doa): 30 April 1995
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 31 October 1995
Date of withdrawal of any conflicting National Standard (dow): 31 October 1995

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ETS 300 177: January 1995
1 Scope
This ETS specifies the data syntax to be used by Videotex services for conveying photographic data.
In general, it applies to the interchange of photographic data via storage or transmission media.
This ETS is applicable to Videotex terminals connected to various types of telecommunication networks
including; a Public Switched Telephone Network (PSTN), a Packet Switched Public Data Network
(PSPDN) or an Integrated Services Digital Network (ISDN). For the ISDN case, these terminals will
typically support "ISDN Syntax-based Videotex" (see ETS 300 079 [3]).
The syntax allows for some private extensions beyond the transmission of still pictures. For example, a
provision has been made for the transmission of a "difference" image to allow a slow scan television type
of application.
2 Normative references
This ETS incorporates by dated or undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed
hereafter. For dated references subsequent amendments to or revisions of, any of these publications
apply to this ETS only when incorporated in it by amendment or revision. For undated references the latest
edition of the publication referred to applies.
[1] ETS 300 072: "Terminal Equipment (TE); Videotex presentation layer protocol,
Videotex presentation layer data syntax".
[2] ETS 300 076: "Terminal Equipment (TE); Videotex, Terminal Facility Identifier
(TFI)".
[3] ETS 300 079 (1991): "Integrated Services Digital Network (ISDN); Syntax-based
Videotex, End-to-end protocols".
[4] CCITT Recommendation F.300 (1988): "Videotex service".
[5] ITU-T Recommendation T.101: "International interworking for videotex
services".
[6] CCITT Recommendation H.261 (1988): "Common intermediate format".
[7] CCITT Recommendation T.51: "Latin based coded character sets for telematic
services".
[8] CCITT Recommendation T.61 (1988): "Character repertoire and coded
character sets for the international teletex service".
[9] CCIR Recommendation 601-1 (1986): "Encoding Parameters of Digital
Television For Studios".
[10] ISO 2022 (1986): "Information Processing - ISO 7-bit and 8-bit coded character
sets - Code extension techniques".
[11] ISO/IEC 9281-1 (1990): "Information technology - Picture coding methods- Part
1: Identification".
[12] ISO/IEC 9281-2 (1990): "Information Technology - Picture coding methods -
Part 2: Procedure for registration".
[13] ISO/IEC 10918-1/ITU-T Recommendation T.81: "Information technology - Digital
compression and encoding of continuous-tone still images - Requirements and
guidelines".
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ETS 300 177: January 1995
[14] ISO 646 (1990): "Information processing - ISO 7-bit coded character set for
information interchange".
[15] ISO 6937 (1991): "Information processing - coded character sets for text
communication".
[16] ISO 2375 (1991): "Data Processing - Procedure for registration of escape
sequences".
[17] ITU-T Recommendation T.4 (1993): "Standardization of group 3 facsimile
apparatus for document transmission".
[18] CCITT Recommendation T.6 (1988): "Facsimile coding schemes and coding
control functions for group 4 facsimile apparatus".
[19] ITU-T Recommendation T.82 (1993): "Information technology - Coded
representation of picture and audio information - Progressive bi-level image
compression".
[20] ITU-T Recommendation T.30 (1993): "Procedures for document facsimile
transmission in the general switched telephone network".
[21] ITU-T Recommendation T.563 (1993): "Terminal characteristics for group 4
facsimile apparatus".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of this ETS the following definitions apply.
aspect ratio: The ratio of the width to the height of a rectangular area, such as the defined display area.
attribute: A particular property or quantity defined in this syntax and described by a number of parameters
(e.g. the source picture specifications).
baseline: The basic sequential DCT-based encoding and decoding process specified in ISO/IEC 10918-1
[13].
continuous tone image: An image comprised of data which exhibits a first order continuity in the
analogue domain and requires, when digitized, more than one bit to describe each sample contained in
one or more of its components (monochrome (grey scale) or colour pictures) e.g., a monochrome image
needs at least 6 bits/picture element (64 grey levels) to appear "continuous" to the eye.
Data Syntax I: Term used within ITU-T for one of the recommended world-wide Videotex data syntaxes
originating from the Japanese Character And Pattern Telephone Access Information Network (CAPTAIN)
system.
Data Syntax II: Term used within ITU-T for one of the recommended world-wide Videotex data syntaxes
originating from the European CEPT Videotex syntax.
Data Syntax III: Term used within ITU-T for one of the recommended world-wide Videotex data syntaxes
originating from the North American Presentation Layer Protocol Syntax (NAPLPS).
Defined Display Area (DDA), Physical (Physical Defined Display Area (DDA)): A rectangular area of
the full screen area where photographic data, text etc. shall be displayed.
Defined Display Area (DDA), Logical (Logical DDA): A unit square, the length of all sides being one
unit, co-ordinates being defined as fractions of unity (unit screen concept). The origin is coincident with the
bottom left corner of the physical DDA and one side is coincident with the longest side of the physical
DDA.
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ETS 300 177: January 1995
Defined Display Area, Source (Source DDA): The virtual display space where the source image was
encoded and which is to be mapped for display either to the full screen area or to the physical DDA.
Discrete Cosine Transformation (DCT): Either the forward discrete cosine transform or the inverse
discrete cosine transform [ISO/IEC 10918-1] .
facsimile picture: A photographic picture, encoded with ITU-T Recommendation T.4 [17] or CCITT
Recommendation T.6 [18] facsimile coding, using the present Videotex Photographic Syntax.
full screen area: The part of a display screen where photographic data can be displayed, it normally
means a display with no borders.
forward DCT: A mathematical transformation using cosine basis functions which converts a block of
samples into a corresponding block of original DCT co-efficients [ISO/IEC 10918-1].
inverse DCT: A mathematical transformation using cosine basis functions which converts a block of
dequantized DCT coefficents into a corresponding block of samples [ISO/IEC 10918-1].
image attribute: The various properties of a continuous tone image described by a number of
parameters.
image data: The data which represents a continuous tone image in digital form, it contains photographic
header data and photographic data.
JPEG compression algorithm: A general term for referring to any one of the possible modes of
encoding defined in ISO/IEC 10918-1 [13].
normalised co-ordinate: A co-ordinate specified in a device independent co-ordinate system, normalised
to some range (usually to 1).
page: See Defined Display Area, Source (Source DDA). If digitized with a facsimile scanner a page is
generally equivalent to the whole facsimile content of an ISO paper sheet format (ISO A4, B4, A3.).
parameter: A quantity which is described using one or more sub-parameters.
photographic data: Pixel based pictorial information usually in compressed digital form; the data includes
any tables which are necessary to decode and decompress the data.
photographic data syntax: The rules by which the photographic header data and the photographic data
are formatted.
photographic header data: Coded data containing the values of the attributes and parameters used for
describing the photographic image.
photographic image: A continuous tone image, e.g. an image represented with 256 shades of grey.
photographic mode: The mode of operation of a Videotex terminal while it is receiving photographic
header data and photographic data.
photographic profile: A collection of attributes with parameters set to a given value to represent a type of
source image and define a mode of photographic image coding and photographic image transfer.
photo Videotex: Neologism used for Videotex photographic mode.
physical device: Any tangible piece of equipment (e.g., personal computer, display monitor, etc.).
pixel, picture element: It is the minimum displayable element of an image (see ISO/IEC 10918-1 [13]).
pixel density: Expresses the number of pixels per physical unit (e.g. pixels/mm) in the horizontal and
vertical directions.
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ETS 300 177: January 1995
pixel density ratio: Ratio between the pixel density in the horizontal direction and the pixel density in the
vertical direction.
post-processing technique: Image processing which is performed (e.g. for display) after the image has
been decoded and decompressed.
spatial resolution: Definition of the size of the image, expressed in the number of pixels per horizontal
line and the number of lines per image.
storage media: A type of physical means to store data.
sub-parameter: A quantity to which a value can be assigned.
NOTE 1: Example of the use of attribute, parameter and sub-parameter. Consider the ISDN, it
has the following attributes, it is digital and supports data transmission with a speed of
64 kbit/s. For the ISDN the parameter network speed is assigned the value 64 kbit/s.
Two sub-parameters can represent this quantity, "numerical speed" i.e., 64 and "unit of
measure" i.e., kbit/s.
spectral content: A physical quantity that measures the frequency content i.e., the amplitude and phase
of each frequency contained in a given physical item. It generally refers to the fourier analysis. For the
Discrete Cosine Transformation (DCT) it relates to the amplitude of each DCT basic function (Discrete
Cosine) or sub-image. In simple terms, for the image, it gives an idea on the "level of detail" of the source
image.
transmission media: The type of physical means to transport data (e.g., coaxial cable, optical fibre, radio
link).
Videotex system: Text communication system, hardware and software, with the capability of running a
Videotex service or application.
Videotex application: P art of a Videotex service which is under the responsibility of only one
provider. The Videotex service provider may also act as an application provider [CCITT Recommendation
F.300] .
Videotex host computer: The computer (or network of computers provided by a single party) on which
one or more applications are implemented and/or one or more other Videotex service facilities are
provided [CCITT Recommendation F.300].
Videotex service: A Videotex service is an interactive service which provides, through appropriate access
by standardized procedures, for users of videotex terminals to communicate with data bases and other
computer based applications via telecommunications networks. The Videotex service includes the
following set of characteristics:
1) information is generally in an alphanumeric and/or pictorial form and may by supplemented by
audio;
2) information is stored in a data base;
3) information is transmitted between the data base and users by telecommunications networks;
4) displayable information is presented on a suitably modified television receiver or other visual display
device;
5) access is under the user's direct or indirect control;
6) the service is easily operated by the general public as well as specialist users, i.e. the service is
user-friendly;
7) the service provides facilities for users to create and modify information in the data bases;
8) the service provides data base management facilities which allow information providers to create,
maintain and manage data bases and to manage closed user group facilities;
9) the service provides computer based applications, e.g., data processing, computer games [CCITT
Recommendation F.300 (1988)].
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ETS 300 177: January 1995
Videotex terminal: The equipment by means of which the user interacts with the Videotex service. A
typical Videotex terminal includes:
1) a numeric keypad and/or alphanumeric keyboard and/or other graphical input devices;
2) a visual display unit or suitably modified television receiver;
3) electronic processing and storage devices required to interface these components to the
telecommunications network and to generate display.
The terminal may also provide a direct terminal-to-terminal capability, and may include other components,
such as a hard copy output unit, magnetic or op
...