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Recommendation I.241 - Teleservices supported by an ISDN
Recommendation I.210 describes the principles for defining telecommunication services supported by an ISDN
including the concept of bearer services, teleservices, and supplementary services. It also provides the means for the
definition and description of such services.
In Recommendation I.240, six teleservices are identified to be supported by an ISDN, i.e., Telephony, Teletex,
Telefax 4, Mixed mode, Videotex and Telex.
This Recommendation contains the service descriptions for these teleservices. Descriptions for other teleservices are
for further study. The description of teleservices is structured in accordance with the three steps in stage 1 of the ser-
vice description method.
The recommended support for these teleservices is given in section 7.2 of each individual service description.
I.241.1 Telephony
1. Definition
The "Telephony Service" provides users with the ability for real-time two-way speech conversation via the network.
2. Description
2.1 General description
The "Telephony service" provides speech transmission at an audio bandwidth of 3.1 kHz. The communication is bidi-
rectional, with both directions continuously and simultaneously active during the speech phase. The network may use
processing techniques appropriate for speech such as analogue transmission, echo cancellation and low bit rate encod-
ing.
The digital signal at the S/T reference point follows the encoding laws for speech (according to Recommendation
G.711), A-law or ╡-law and the network may use digital signal processing techniques. It may also be necessary to use
echo cancellation techniques in particular when interworking with other networks such as the PSTN. User information is
provided over a B channel, signalling is provided over the Dchannel. Tones and announcements are provided by the net-
work, encoded according to Recommendation G.711, although terminals can generate tones or other indications based
on the messages received.
2.2 Specific terminology
a) Voice quality
The required acoustic performance is described in terms of loudness ratings, frequency response,
quantizing distortion, etc. Overall requirements are given in the Recommendations in the P-
Series.
b) Transmission delay
The maximum delay is that specified for the general telephone network (cf. Recommendation G.114). The per-
missible variation of the actual delay is for further study.
c) Retention Timer
This timer specifies the amount of time that the network retains the call information of the original call upon
encountering busy or being released. This timer is a network provider option. The value for this timer is greater
than 15 seconds.
3. Procedures
3.1 Provision/withdrawal
3.1.1 Provision of this service will be by pre-arrangement with the administration/RPOA.
3.1.2 The teleservice is offered with several subscription options which apply separately to each ISDN number or group
of ISDN numbers on the interface. For each subscription option, only one value can be selected. Subscription options
for the interface are summarized below:
Subscription Option Value
Maximum number of information m, where m is not greater
channels available at user B than the number of
information channels on the
interface
Maximum number of total calls n, where n is not greater
present at user B than the number of
information channels on the
interface
User B can be an ISDN number or group of ISDN numbers on the interface.
Note - More than one ISDN number can be associated with the service/interface only as a part of a supplementary service
such as multiple subscriber number. In the case of one ISDN number, the option given above for the number of calls can
only exceed the number of information channels in association with a supplementary service (e.g. call waiting). As a net-
work provider option, separate values may be specified for incoming and for outgoing calls for either or both of the limits.
3.2 Normal procedures
a) Originating the service (call set up)
The service is originated by the originating user activating the terminal, performing service selection if applicable for
the originating terminal, and terminating customer selection. During this process the originating user is given appropriate
indications as to the state of the call.
1) a service selection is required on a multi-service terminal;
2) terminating customer selection is selecting the required termination (user/network interface) by an
appropriate means (for example, the use of DDI, or multiple subscriber number);
3) indications during call origination may include an indication that the network is ready to receive the
network address information (proceed indication) and an indication that the call is progressing through the network. It
shall be possible to have audibleindications which may be accompanied by other indications.
b) Call acceptance (answer)
Selection of the terminating customer is indicated to each user by appropriate indications (call arrival indication and
awaiting answer indication). The acceptance of the call by the terminating user, i.e., answer, causes the indications to be
removed and bidirectional communication paths to be provided. The call is now termed in the "speech phase".
c) Call release
A request to terminate the service may be generated by either user. If one user terminates the service the other user
is given an appropriate indication as to the state of the call.
d) Failure situations due to user error
The following failure situations may occur due to user error:
1) user taking too long to input the network address information will be given as a failure indication, e.g.
during overlap sending (see Recommendations I.451 and I.220);
2) user inputting a non valid network address, e.g. an unallocated address, will be given a failure indica-
tion.
e) Failure indications due to terminating termination state
1) User attempting to set up a call to a termination where no free B channels are available will receive a
busy indication unless call waiting or another supplementary service is in operation (Note 1).
Note 1 - In support of some supplementary services (e.g. call waiting, line hunting), it may optionally be necessary for the
subscriber to register some additional parameters (e.g. destination number used to distinguish PSTN telephony calls) with
the network to allow the network to know when a channel is busy with telephony.
2) User attempting to set up a call to a termination where the call is not accepted, i.e. no response indi-
cating call acceptance is received, will after a defined period be given a call failure indication. (See
Recommendations I.451 and I.220).
f) Failure situations due to network conditions
1) User attempting to set up a call but meeting problems in the network (e.g. congestion) will be given a
suitable indication.
4. Network capabilities for charging
This Recommendation does not cover charging principles. Future Recommendations in the D-Series are expected to
contain that information. It shall be possible to charge the subscriber accurately for the service.
5. Interworking requirements
5.1 Interworking is required between the ISDN and PSTN.
6. Interaction with supplementary services
Not applicable. Each supplementary service description identifies the applicability with this teleservice.
7. Attributes/values
7.1 a) Low layer attributes
Information transfer attributes
1. Information transfer mode: Circuit
2. Information transfer rate: 64 kbit/s
3. Information transfer capability: Speech
4. Structure: 8 kHz integrity
5. Establishment of communication: on demand
6. Communication configuration: Point-to-point
7. Symmetry: Bidirectional symmetric
Access attributes
Access channel (and rate): B(64) for user information, D for signalling (Note 2)
9.1 Signalling access protocol layer 1: I.430/I.431
9.4 Information access protocol layer 1: I.430/I.431; G.711
9.2 Signalling access protocol layer 2: I.440/I.441
9.5 Information access protocol layer 2: -
9.3 Signalling access protocol layer 3: I.450/I.451
9.6 Information access protocol layer 3: -
Note 2 - For reserved/permanent service the operational, administrative and maintenance message related to these ser-
vices may be conveyed over the Dchannel.
b) Higher layer attributes
10. Type of user information: Speech
11. Layer 4 protocol functions: -
12. Layer 5 protocol functions: -
13. Layer 6 protocol functions: G.711
14. Layer 7 protocol functions: -
c) General attributes
15. Supplementary services provided:FS
16. Quality of Service: FS
17. Interworking possibilities: to and from PSTN
18. Operational and commercial: FS
- Not applicable
FS for further study
7.2 Telephony supported by an ISDN
In the following table the recommended overall support, and recommended support for the variations of the
non-dominant attributes are given. The definition of E (essential) and A (additional) can be found in Recommen-
dationI.240.
a) Overall support: E/A (Note 3)
Variations of non-dominant attributes:
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b1)|Information transfer mode | Support |
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| circuit | E |
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b2)| Establishment | Symmetry |Communication | Support |
| of communication | |configuration | |
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| demand | | pt-pt | E |
| reserved |Bidirectional | pt-pt | FS |
| permanent | Symmetric | pt-pt | A |
| | | | |
| demand | | multipt | A |
| reserved |Bidirectional | pt-pt | FS |
| permanent | Symmetric | multipt | A |
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b3) Access:
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| Signalling and OAM |User information | Support |
| (Note 4) | | |
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| Channel | Protocols |Channel |Protocols| |
| and rate | |and rate | | |
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| D(16) |I.430, I.440, | B(64) |I.430, | E |
| |I.441, I.450, | |G.711 | |
| |I.451 (Note 5)| | | |
| | | | | |
| D(64) |I.431, I.440, | B(64) |I.431, | E |
| |I.441, I.450, | |G.711 | |
| |I.451 (Note 5)| | | |
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Note 3 - It is anticipated that ISDNs offer telephony as a basic telecommunication service. Some networks will offer
this as a teleservice. However, due to national regulation policies some networks will offer telephony as a bearer
service rather than as a teleservice.
Note 4 - Definition of protocols for OAM are FFS.
Note 5 - Demand services only. Others are FFS.
8. Dynamic description
The circuit-mode dynamic description appears in RecommendationI.220.
I.241.2 Teletex
The prose description of the Teletex service is an extract of Recommendation F.200. If more detail is required
this Recommendation should be referred to. As such, this service description does not strictly follow the substeps for
step 1.1 of the service description method. Further alignment with the substeps requires further study.
1. Definition
Teletex is an international service, enabling subscribers to exchange office correspondence in the form of docu-
ments containing Teletex coded information on an automatic memory-to-memory basis via the ISDN.
2. Description
2.1 Scope
The Teletex service provides communication between Teletex equipment* which are used for the preparation,
editing and printing of correspondence containing text information using a standardized character set (Recommen-
dationT.61).
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*Teletex equipment may be a Teletex terminal or a system.
The basic element of the correspondence between people using the service is the page, as the smallest unit of text
treated as an entity. No restrictions shall exist as far as the operator procedures for generation of the text or the position-
ing of text within the printable area on a page are concerned.
Note 1 - This does not necessarily imply that the characters used to construct a graphic symbol are transmitted in the
same sequence as that in which they are keyed.
Note 2 - This does not necessarily imply that the order in which text on a page is transmitted is the same as that in which
it was keyed.
Note 3 - An exception to this rule is the application of the processable mode of operation for which the page as a basic
element of correspondence cannot be used. The processable mode of operation within the Teletex service is defined in Rec-
ommendation F.220.
2.2 Operation
2.2.1 General
The Teletex service in each country and the international interconnection between countries or networks shall use auto-
matic switching so that it is possible for any Teletex subscriber to reach any other Teletex subscriber using fully automatic
selection.
It is a requirement to allow the through-connection of a call between a Teletex terminal connected to a private auto-
matic branch exchange (or similar systems) and those connected to public exchanges used for the Teletex service.
A virtual dialogue mode of operation, which appears to the subscriber as an interactive mode should be possible,
although this is not a basic requirement of the Teletex service.
A virtual dialogue mode of operation, which appears to the subscriber as an interactive mode may become possible as a
new standardized option within the Teletex service, both allowing communications between persons and data base access
(refer to Recommendation I.210).
Processable mode of operation, as a standardized option within the Teletex service, allows the transfer of text containing
information to permit convenient further editing and processing by the recipient (refer to Recommendation F.220).
Mixed mode of operation using the techniques of Telefax 4 for the transfer of facsimile-coded information and of Tele-
tex for the transfer of character-codedtext is described as a standardized option within the Teletex service in Recommen-
dation F.230.
Two-way alternate (TWA) communication is a capability of the Teletex service, which also includes one-way communica-
tion (OWC); the calling subscriber will have full control of the Teletex call.
3. Procedures
3.1 Provision/withdrawal
The national and international facilities of the Teletex service, including the Teletex/telex conversion facilities, shall be
open continuously.
Teletex subscriber equipment for which call numbers are published in the directories shall, in principle, be available to
accept calls continuously.
In order to facilitate the twenty-four hour duration of the service it is permitted to use a centralized storage in the net-
work to realize receiving memory capability of the terminal.
3.2 Call phases
The operations for each call may be divided into the following three phases:
a) Preparation
- preparation of the information in local mode;
- loading of the information into a memory,
b) Transmission (in principle, automatic)
- call establishment;
- pre-information phase (see note);
- information transfer from memory-to-memory (see note);
- post information phase (see note);
- call clearing.
Note - During these parts of the transmission phase the network must be transparent with respect to control procedures.
c) Output
- emptying the memory.
Note - The information may consist of one or more Teletex documents each consisting of one or more Teletex pages.
The control procedures as specified in Recommendation T.62 shall be used as end-to-end communication procedures
between any Teletex equipment in the basic service.
The lower layer protocols and the network independent basic transport protocol to be used for Teletex are specified in
RecommendationsT.70 and T.90.
The network-dependent control procedures for the Teletex are those that are defined for ISDN.
3.3 Call identification line
The Teletex procedures include the exchange of reference information prior to sending any document. This reference
information includes identification of the parties to the call as well as the date and time. Also, supplementary reference
information is exchanged during a call to allow reference to an individual document or page for error recovery or other pur-
poses.
This reference information, taken together, is defined to be printable on a single line called the call identification line. The
use of this information is a local decision except in recovering from an interrupted transmission.
The Call Identification Line is composed of four fields as follows:
- Field 1: identification of the called Teletex equipment;
- Field 2: identification of the calling Teletex equipment;
- Field 3: date and time;
- Field 4: supplementary reference information.
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| Field 1 | | Field 2 | | Field 3 | | Field 4 |
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| Identification | | Identification | |Date and time | |Supplementary |
| of the called |/| of the calling |/| |/| reference |
| Teletex equipment | |Teletex equipment| | | | information |
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| 24 characters |1|24 characters |1|14 characters |1| 7 characters |
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<ûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûû 72 Characters ûûûûûûûûûûûûûûûûûûûûûûûûûûûû>
T1807030-88
Field 1 - (identification of the called equipment) contains the identification of the called equipment. It is originated in
the control procedures by the called equipment.
Field 2 - (identification of the calling equipment) contains the identification of the calling equipment. It is originated in
the control procedures by the calling equipment.
Field 3 - (date and time) contains the date and time reference information showing the year, month, day, hour and
minute in the fixed format of 14characters thus YY-MM-DD-HH:MM. This field is originated in the control procedures by the
calling equipment which obtains this information from the network. This time represents the local time at the calling equip-
ment and is intended to represent the time of call origination.
Field 4 - (supplementary reference information) contains a document reference number, a hyphen (coding 2/13) as a
separator and a page reference number as defined in Recommendation T.62. This field has a fixed length of seven character
positions and is originated in the control procedures by the Teletex equipment that is sending the associated documents.
FIGURE 1/I.241.2
Format of the Call Identification Line
3.4 Error protection
Within the Teletex service a high layer error detection and correction is provided in the session layer for all those errors
which are not corrected by the network layers.
To ensure call integrity, error protection will be provided by Teletex control procedures (see Recommendations T.62, T.70
and T.90). The error rate on the pre-information, information and post-information phases should not exceed 1 in 106
characters.
4. Network capabilities for charging
This Recommendation does not cover charging principles. Future Recommendations in the D-Series are expected to
contain that information. It shall be possible to charge the subscriber accurately for the service.
5. Interworking requirements
5.1 Within the Teletex service interworking between terminals connected to different networks is required. Real-time connec-
tion between terminals operating at different speeds has to be provided on the basis of at least 2.4kbit/s.
5.2 Intercommunication with other services
5.2.1 The Teletex service will provide the ability to intercommunication both directions with the telex service by means of
conversion facilities (refer to RecommendationsF.201, U.201, T.390).
5.2.2 Intercommunication between basic mode and mixed mode Teletex terminals and ClassesI, II and III Group4 facsimile
terminals is shown in Table1 (refer to Recommendation F.184).
5.2.3 The Teletex service allows for intercommunication with telex and with Interpersonal Messaging Service (IPM) (Ref. to
F.421, F.422).
TABLE 1/I.241.2
Current status of direct intercommunication for Teletex and
Group 4 facsimile terminals on the same network
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| To |Facsimile | Facsimile | Facsimile | Teletex | Teletex | Teletex |
| |Group 4 | Group 4 | Group 4 | basic | mixed | Processable|
| From |Class I | Class II | Class III | mode | mode | Mode 1 |
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|Facsimile| | | | | | |
|Group 4 | F | F | F | | | |
|Class I | | | | | | |
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|Facsimile| | | | | | |
|Group 4 | F | F | F | | | |
|Class II | | | | | | |
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|Facsimile| | | | | | |
|Group 4 | F | T, F, MM | T, F, MM | T | T, MM | T |
|Class III| | | | | | |
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|Teletex | | | | | | |
|basic | | T | T | T | T | T |
|mode | | | | | | |
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|Teletex | | | | | | |
|mixed | |T, MM|T, MM| T | T, MM | T |
|mode | | | | | | |
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|Teletex | | | | | | |
|Proces- | | T | T | T | T | T, PM1 |
|sable | | | | | | |
|Mode 1 | | | | | | |
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T: Basic Teletex document with character coded information only.
F: Group 4 Facsimile document with facsimile coded information only.
MM: Mixed-mode document with character and facsimile coded information.
PM1: Processable mode document with character coded information only.
6. Interaction with supplementary services
Each supplementary service description identifies the applicability with this teleservice.
For the ISDN, the international supplementary services which may be used for Teletex in the circuit mode using a B
Channel:
i) Closed User Group;
ii) Multiple Subscriber Number;
iii) User-to-User Signalling;
iv) Calling Line Identification Presentation;
v) Calling Line Identification Restriction;
vi) Connected Line Identification Presentation;
vii) Connected Line Identification Restriction;
viii) Direct Dialling In;
The use of other supplementary services is for further study.
Supplementary Services for Teletex with packet mode of operation are for further study.
7. Attributes/values
7.1 a) Low layer attributes
Information transfer attributes
Circuit mode bearer Packet mode bearer capability
capability
1. Mode: Circuit Packet
2. Rate: 64 kbit/s Maximum throughput of a
given virtual circuit is
less than or equal to the
maximum bit rate of the
user information access
channel and the throughput
class of the virtual
circuit.
3. Info transfer Unrestricted (Note 4) Unrestricted
cap:
4. Structure: Unstructured (Note 5) Service data unit
integrity
5. Establishment: Demand Demand (VC), permanent (PVC)
6. Configuration: Point-to-point Point-to-point
7. Symmetry: Bidirectional symmetric Bidirectional symmetric
Access attributes
Circuit mode bearer Packet mode bearer capability
capability
8. Access B Channel User information over
channel: (B for user info. virtual circuit within B or
D for signalling) D Channel. When D Channel is
used, maximum packet size and
quality of service may be
restricted. Signalling may be
provided via D and/or virtual
circuit within B Channel.
9.1 Signalling I.430/I.431 I.430/I.431
access protocol
layer 1:
9.2 Signalling I.440/I.441 I.440/I.441, X.31
access protocol
layer 2:
9.3 Signalling I.450/I.451 I.450/I.451, X.31
access protocol
layer 3:
9.4 Information I.430/I.431 I.430/I.431
access protocol
layer 1:
9.5 Information X.75 (SLP) X.25 LAP B
access protocol
layer 2:
9.6 Information ISO 8208 X.25 (PLP)
access protocol
layer 3:
Note 4 - The interworking arrangements with networks having restricted 64kbit/s information transfer capability require fur-
ther study.
Note 5 - Even if no structure is required the network may provide 8kHz integrity.
b) High layer attributes
10. Type of user info: Teletex
11. Layer 4 protocol: T.70
12. Layer 5 protocol: T.62
13. Layer 6 protocol: T.61
14. Layer 7 protocol: T.60
c) General attributes
15. Supplementary services provided: See sub-section 6/I.241.2
16. Quality of service: FS
17. Interworking possibilities: See sub-section 5/I.241.2
18. Operational and commercial: FS
SLP - Single Link Protocol
PLP - Packet Layer Protocol
7.2 Teletex supported by an ISDN
In the following table the recommended overall support, and recommended support for the variations of the non-domi-
nant attributes are given. The definition of E (Essential) and A (Additional) can be found in RecommendationI.240.
a) Overall support: A
b) Variations of non-dominant attributes:
b.1) Information transfer mode (Note 6) | Support
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circuit | A
packet | A
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b.2) Establishment Symmetry Communication | Support
of communication configuration |
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demand bidirectional pt-pt | E
symmetric |
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|
b.3) Access: |
| |
Signalling & OAM | User information | Support
(Note 7) | |
| |
Channel| | Channel | |
& rate | Protocols | & rate | Protocols |
ûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûûûûûûûû+ûûûûûûûûûûûû
Circuit mode
D(16) | I.430, I.440, I.441, | B(64) | I.430, | A
| I.450, I.451 (Note 8) | | X.75 (SLP), |
| | | ISO 8208 |
| | | |
D(64) | I.431, I.440, I.441, | B(64) | I.431, | A
| I.450, I.451 (Note 8) | | X.75 (SLP), |
| | | ISO 8208 |
ûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûûûûûûûû+ûûûûûûûûûûûû
Packet mode
D(16) | I.430, I.440, I.441, | B(64) | I.430, | A
| I.450, I.451, X.31 | of | X.25 LAP B, |
| | D(16) | X.25 (PLP) |
| | | |
D(64) | I.431, I.440, I.441, | B(64) | I.431, | FS
| I.450, I.451, X.31 | | X.25 LAP B, |
| | | X.25 (PLP) |
| | | |
VC in | FS | B(64) | FS | FS
B(64) | | | |
ûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûûûûûûûû+ûûûûûûûûûûûû
Note 6 - In the interim period the circuit-mode method of operation is preferred.
Note 7 - Definition of protocols for OAM are FFS
Note 8 - Demand services only. Other are FFS.
8. Dynamic description
The circuit-mode dynamic description appears in RecommendationI.220.
I.241.3 Telefax 4
The prose description of the Telefax 4 service is an extract of RecommendationF.184. If more detail is required this Rec-
ommendation should be referred to. As such this service is not strictly structured a wording to the substeps for Step1.1 of
the service description method. Further alignment with the substeps requires further study.
1. Definition
Telefax4 is an international service enabling subscribers to exchange office correspondence in the form of documents
containing facsimile coded information automatically via the ISDN.
2. Description
2.1 General description
The Telefax 4 service provides a basic level of compatibility between all terminals participating in the service. It
offers bidirectional communication between two users via the ISDN using 64kbit/s digital signals over the B channel.
There are three classes of Group4 facsimile terminals:
Class I - minimum requirement terminal is a terminal able to send and receivedocuments containing facsimile
encoded information (in accordance with RecommendationsT.6 and T.400-Series).
Class II - minimum requirement terminal is a terminal able to transmit documents that are facsimile encoded
(in accordance with RecommendationsT.6 and T.400-Series). In addition, the terminal must be capable of receiv-
ing documents which are facsimile coded (in accordance with RecommendationsT.6 and T.400-Series), teletex
coded (in accordance with the basic coded character repertoire and defined in RecommendationT.61) and also
mixed-mode documents (in accordance with Recommendationsof the T.400-Series).
Class III - minimum requirement terminal is a terminal that is capable of generating, transmitting and receiving
facsimile coded documents (in accordance with RecommendationsT.6 and T.400-Series), teletex coded documents
(in accordance with the basic coded character repertoire as defined in RecommendationT.61) and mixed-mode
documents (in accordance with Recommendationsof the T.400-Series).
The basic element of the correspondence between people using the service is the page, as the smallest unit of
text treated as an entity.
No restrictions shall exist as far as the operator procedures for generation of the text or the positioning of text within
the reproducible area on a page are concerned.
3. Procedures
3.1 Provision/withdrawal
The national and international Telefax4 service shall be open continuously.
Telefax4 terminals for which call numbers are published in the directories shall, in principle, be available to accept
calls continuously.
In order to facilitate the 24 hour duration of service it is permitted to use a centralized storage in the network to
realize receiving memory capability of the terminal.
3.2 General
The Telefax4 service in each country and the interconnection between countries or networks shall use automatic
switching so that it is possible for any Telefax4 subscriber to reach any other Telefax4 subscriber using fully automatic
selection.
It is a requirement to allow the through-connection of a call between Group4 facsimile terminals connected to a
private automatic branch exchange (or similar systems) and those connected to public exchanges used for the Group4
facsimile service.
Two-way alternate (TWA) communication is a capability of the Telefax4 service, which also includes one-way com-
munication (OWC); the calling subscriber will have full control of the Group4 facsimile call.
3.3 Call phases
The operations for each call may be divided into the following three phases:
a)preparation: preparation of the information to be transmitted;
b)transmission:
-call establishment (automatic);
-pre-information phase (see Note);
-information transfer (see Note);
-post information phase (see Note);
-call clearing.
Note - During these parts of the transmission phase the network must be transparent with respect to control pro-
cedures.
c)output: displaying the message either by immediate printing or from a storage medium upon control by the
operator.
Note - The information may consist of one or more Telefax4 documents each consisting of one or more Telefax pages.
The control procedures as specified in the Recommendations of the T.400-Series and T.62 shall be used as end-
to-end communication procedures between terminals in the service.
The low layer protocols and the network independent basic transport protocol for Telefax4 are specified in Recom-
mendations T.70 and T.90.
The network dependent control procedures for the Telefax4 service are those that are defined for ISDN.
3.4 Call identification
The Telefax4 procedures include the exchange of reference information prior to sending any document. This refer-
ence information includes identification of the parties to the call as well as the date and time. Also, supplementary ref-
erence information is exchanged during a call to allow reference to an individual document or page for error recovery
or other purposes. Date and time have to be provided by the network and sent to the calling terminal in the call set up
phase.
This reference information, taken together, is defined to be printable on a single line called the call identification
line. Use of this information is a local decision except in recovering from an interrupted transmission. In the case of
automatic linking, the use of this information is for further study.
For the format of the call identification line: see RecommendationF.200.
3.5 Error protection
To ensure call integrity, error protection will be provided by Telefax4 control procedures (see RecommendationsT.62,
T.70 and T.90). Besides the error detection and correction mechanism in the layer 2 (and 3) an additional error detec-
tion and correction mechanism is provided in the session layer. By this mechanism errors of the higher layer functions
(e.g. command/response sequence error) and transmission errors, which are not corrected by the lower layers, will be
corrected by e.g. retransmission of one or several pages.
The error rate on the pre-information, information and post-information phases should not exceed 1x10-6.
4. Network capabilities for charging
This Recommendation does not cover charging principles. Future Recommendations in the D-Series are expected to
contain that information. It shall be possible to charge the subscriber accurately for the service.
5. Interworking requirements
5.1 Within the Telefax4 service interworking between terminals connected to different networks is required
a)Telefax 4 (ISDN) - Telefax 4 (CSPDN)
b)Telefax 4 (ISDN) - Telefax 4 (PSPDN)
c)Telefax 4 (ISDN) - Telefax 4 (PSTN)
In the case of international interworking between Group4 facsimile terminals connected to dissimilar networks, Rec-
ommendationX.300 shall
apply. For international interworking between PSTN and ISDN, a (separate) Telefax4 interworking unit may be necessary.
International routes between ISDNs for the Telefax4 service shall be capable of supporting user data rates up to
64kbit/s.
5.2 Intercommunication with other services
5.2.1 Intercommunication between basic mode and mixed mode Teletex terminals and ClassesI, II and III Group4 facsimile
terminals connected to the Telefax4 service is shown in Table1/I.241.3.
TABLE 1/I.241.3
Current status possible cases of direct intercommunication for Teletex
and Group 4 facsimile terminals
on the same network
+ûûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+
| | | | | | |Teletex|
| To |Facsimile|Facsimile|Facsimile|Teletex |Teletex|proces- |
|From |Group 4 |Group 4|Group 4|basic |mixed|sable |
| | Class I | Class II |Class III |mode|mode|Mode 1 |
+ûûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+
|Facsimile |||||| |
|Group 4 | F | F | F | | | |
|Class I | | | | | | |
+ûûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+
|Facsimile | | | | | | |
|Group 4|F|F|F|| | |
|Class II | | | | | | |
+ûûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+
|Facsimile | | | | | | |
|Group 4|F|T, F, MM|T, F, MM|T |T, MM|T |
|Class III | | | | | | |
+ûûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+
|Teletex | | | | | | |
|basic||T|T|T |T|T |
|mode | | | | | | |
+ûûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+
|Teletex | | | | | | |
|mixed | |T, MM|T,MM|T |T,MM|T |
|mode | | | | | | |
+ûûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+
|Teletex | | | | | | |
|Processable| | T | T | T | T | T, PM1 |
|Mode 1 | | | | | | |
+ûûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûû+
T: Basic Teletex document with character coded information only.
F: Group 4 Facsimile document with facsimile coded information only.
MM:Mixed-mode document with character and facsimile coded information.
PM1:Processable mode document with character coded information only.
In both the Teletex and Telefax4 services, the equipment providing mixed mode should enable a direct exchange of
documents in accordance with RecommendationsT.6, T.61 and T.400-Series.
5.2.2 Intercommunication is desirable between terminals of the Telefax4 service and terminals of services other than
Telefax 4 provided over ISDN and other public switched networks.
Intercommunication possibilities between Telefax4 terminals and Telefax3 terminals have to be provided (see also
RecommendationF.180):
a)Telefax 4 (ISDN) - Telefax 3 (PSTN);
b)Telefax 4 (ISDN) - Telefax 3 (ISDN, via terminal adaptors).
In case a) Telefax4 terminals use specific service features in ISDN. Intercommunication should be supported by
ISDN-PSTN interworking units.
In case b) Telefax3 terminals and Telefax4 terminals which are to be connected in the PSTN can also be connected
to the ISDN via terminal adaptors.
6. Interaction with supplementary services
Each supplementary service description identifies the applicability with this teleservice.
International supplementary services for the Telefax4 service in the circuit mode on a B channel:
i)Closed User Group;
ii)Multiple Subscriber Number;
iii) User to User Signalling;
iv)Calling Line Identification Presentation;
v)Calling Line Identification Restriction;
vi)Connected Line Identification Presentation;
vii) Connected Line Identification Restriction;
viii) Direct Dialling In.
The use of other supplementary services is for further study. Supplementary services for Telefax4 with packet
mode of operation are for further study.
7. Attributes/values
7.1 a) Low layer attributes
Information transfer attributes
Circuit mode bearer Packet mode bearer capability
capability
1. Mode: Circuit Packet
2. Rate: 64 kbit/s Maximum throughput of a
given virtual circuit is
less than or equal to the
maximum bit rate of the
user information access
channel and the throughput
class of the virtual
circuit.
3. Info transfer Unrestricted (Note 3) Unrestricted
cap:
4. Structure: Unstructured (Note 4) Service data unit
integrity
5. Establishment: Demand Demand (VC), permanent (PVC)
6. Configuration: Point-to-point Point-to-point
7. Symmetry: Bidirectional symmetric Bidirectional symmetric
Access attributes
Circuit mode bearer Packet mode bearer capability
capability
8. Access B Channel User information over
channel: (B for user info virtual circuit within B or
D for signalling) D Channel. When D Channel is
used, maximum packet size and
quality of service may be
restricted. Signalling may be
provided via D and/or virtual
circuit within B Channel
(Note 1).
9.1 Signalling I.430/I.431 I.430/I.431
access protocol
layer 1:
9.2 Signalling I.440/I.441 I.440/I.441, X.31
access protocol
layer 2:
9.3 Signalling I.450/I.451 I.450/I.451, X.31
access protocol
layer 3:
9.4 Information I.430/I.431 I.430/I.431
access protocol
layer 1:
9.5 Information X.75 (SLP) X.25 LAP B
access protocol
layer 2:
9.6 Information ISO 8208 X.25 (PLP)
access protocol
layer 3:
b) High layer attributes
10. Type of user info: Teletex
11. Layer 4 protocol: T.70
12. Layer 5 protocol: T.62
13. Layer 6 protocol: T.400-Series (Note 2)
13.1Resolution [ppi]: 200 x 200 standard;
240 x 240, 300 x 300, 400 x 400 optional
14. Layer 7 protocol: T.503, 521, 563
c) General attributes
15. Supplementary services provided: see section 6/I.241.3
16. Quality of service: FS
17. Interworking possibilities: see section 5/I.241.3
18. Operational and commercial: FS
Note 1 - User information transferred via virtual channel on the D Channel is for further study.
Note 2 - Further study is required to identify a more precise reference in the T.400-Series of Recommendations.
Note 3 - The interworking arrangements with networks having restricted 64kbit/s information transfer capability require fur-
ther study.
Note 4 - Even if no structure is required the network may provide 8kHz integrity.
7.2 Telefax 4 supported by an ISDN
In the following table the recommended overall support, and recommended support for the variations of the non-domi-
nant attributes are given. The definition of E (Essential) and A (Additional) can be found in RecommendationI.240.
a) Overall support: A
b) Variations of non-dominant attributes:
b.1) Information transfer mode (Note 5) | Support
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circuit | A
packet |
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b.2) Establishment | Symmetry | Communication | Support
of communication | | configuration |
ûûûûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûûûû
demand | bidirectional | pt-pt | E
| symmetric | |
ûûûûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûûûû
|
b.3) Access: |
| |
Signalling & OAM | User information | Support
(Note 6) | |
ûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûûûûûûûû+ûûûûûûûûûûûû
Channel| | Channel | |
& rate | Protocols | & rate | Protocol |
ûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûûûûûûûû+ûûûûûûûûûûûû
| | |
Circuit mode | | |
| | |
D(16) | I.430, I.440, I.441, | B(64) | I.430, | A
| I.450, I.451 (Note 7) | | X.75 (SLP), |
| | | ISO 8208 |
| | | |
D(64) | I.431, I.440, I.441, | B(64) | I.431, | A
| I.450, I.451 (Note 7) | | X.75 (SLP), |
| | | ISO 8208 |
ûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûûûûûûûû+ûûûûûûûûûûûû
Packet mode
D(16) | I.430, I.440, I.441, | B(64) | I.430, | A
| I.450, I.451, X.31 | or | X.25 LAP B, |
| | D(16) | X.25 (PLP) |
| | | |
D(64) | I.431, I.440, I.441, | B(64) | I.431, ... | FS
| I.450, I.451, X.31 | | |
| | | |
| | | |
VC in | FS | B(64) | FS | FS
B(64) | | | |
ûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûûûûûûûû+ûûûûûûûûûûûû
Note 5 - In the interim period the circuit mode method of operation is preferred.
Note 6 - Definition of protocols for OAM is for further study.
Note 7 - Demand services only. Others are FFS.
8. Dynamic description
The circuit mode dynamic description appears in RecommendationI.220.
I.241.4 Mixed mode
The prose definition of the mixed mode service is an extract of Recommendation F.230.
1. Definition
This service provides combined text and facsimile communication for end-to-end transfer of documents containing
mixed information of text and fixed images.The high layer attributes are based on the CCITT Recommendations for Teletex
amd Telefax 4.
2. Description
For further study.
3. Procedures
For further study.
4. Network capabilities for charging
This Recommendation does not cover charging principles. Future Recommendations in the D-Series are expected to
contain that information. It shall be possible to charge the subscriber accurately for the service.
5. Interworking requirements
For further study.
6. Interaction with supplementary services
For further study.
7. Attributes/values
7.1 a) Low layer attributes
Information transfer attributes
Circuit mode bearer Packet mode bearer capability
capability
1. Mode: Circuit Packet
2. Rate: 64 kbit/s Maximum throughput of a
given virtual circuit is
less than or equal to the
maximum bit rate of the
user information access
channel and the throughput
class of the virtual
circuit.
3. Info transfer Unrestricted (Note 2) Unrestricted
cap:
4. Structure: Unstructured (Note 3) Service data unit
integrity
5. Establishment: Demand Demand (VC), permanent (PVC)
6. Configuration: Point-to-point Point-to-point
7. Symmetry: Bidirectional symmetric Bidirectional symmetric
Access attributes
Circuit mode bearer Packet mode bearer capability
capability
8. Access B Channel User information over
channel: (B for user info virtual circuit within B or
D for signalling) D Channel. When D Channel is
used, maximum packet size and
quality of service may be
restricted. Signalling may be
provided via D and/or virtual
circuit within B Channel
(Note 1).
9.1 Signalling I.430/I.431 I.430/I.431
access protocol
layer 1:
9.2 Signalling I.440/I.441 I.440/I.441, X.31
access protocol
layer 2:
9.3 Signalling I.450/I.451 I.450/I.451, X.31
access protocol
layer 3:
9.4 Information I.430/I.431 I.430/I.431
access protocol
layer 1:
9.5 Information X.75 (SLP) X.25 LAP B
access protocol
layer 2:
9.6 Information ISO 8208 X.25 (PLP)
access protocol
layer 3:
b) High layer attributes
10. Type of user info:Mixed mode
11. Layer 4 protocol: X.224, X.214
12. Layer 5 protocol: X.225, X.215
13. Layer 6 protocol: T.61, X.226, X.216X.226, X.216
13.1Resolution [ppi]:300 x 300
240 x 240
400 x 400 optional,
600, 1200
14. Layer 7 protocol:T.501, T.522, T.561
c) General attributes
15. Supplementary services provided: FS
16. Quality of service: FS
17. Interworking possibilities: ISDN Teletex, ISDN Telefax 4;
others: FS
18. Operational and commercial: FS
Note 1 - User information transferred via virtual channel on the D Channel is forfurther study.
Note 2 - The interworking arrangements with networks having restricted 64kbit/s information transfer capability
require further study.
Note 3 - Even if no structure is required the network may provide 8kHz integrity.
7.2 Mixed mode supported by an ISDN
In the following table the recommended overall support, and recommended support for the variations of the
non-dominant attributes are given. The definition of E (Essential) and A (Additional) can be found in Recommen-
dationI.240.
a) Overall support: A
b) Variations of non-dominant attributes:
b.1) Information transfer mode | Support
ûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûûûû
circuit | A
packet | A
ûûûûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûûûû
b.2) Establishment | Symmetry | Communication | Support
of communication | | configuration |
ûûûûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûûûû
demand | bidirectional | pt-pt | E
| symmetric | |
b.3) Access:
| |
Signalling & OAM | User information | Support
(Note 4) | |
ûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûûûûûûûû+ûûûûûûûûûûûû
Channel| | Channel | |
& rate | Protocols | & rate | Protocols |
ûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûûûûûûûû+ûûûûûûûûûûûû
Circuit mode
D(16) | I.430, I.440, I.441, | B(64) | I.430, | A
| I.450, I.451 (Note 5) | | X.75(SLP), |
| | | ISO 8208 |
| | | |
D(64) | I.431, I.440, I.441, | B(64) | I.431, | A
| I.450, I.451 (Note 5) | | X.75(SLP), |
| | | ISO 8208 |
ûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûûûûûûûû+ûûûûûûûûûûûû
Packet mode
D(16) | I.430, I.440, I.441, | B(64) | I.430, | FS
| I.450, I.451, X.31 | or | X.25 LAP B, |
| | D(16) | X.25(PLP) |
| | | |
D(64) | I.431, I.440, I.441, | B(64) | I.431, ... | FS
| I.450, I.451, X.31 | | |
| | | |
VC in | FS | B(64) | FS | FS
B(64) | | | |
ûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûûûûûûûû+ûûûûûûûûûûûû
Note 4 - Definition of protocols for OAM are FFS.
Note 5 - Demand services only. Others are FFS.
8. Dynamic description
The circuit mode dynamic description appears in Recommendation I.220.
I.241.5 Videotex
The prose description for the Videotex service in ISDN is for further study and is intended to be based on Recom-
mendation F.300.
1. Definition
The Videotex service in the ISDN is an enhancement of the existing Videotex service with retrieval and mailbox func-
tions for text (alpha) and graphic information.
2. Description
For further study.
3. Procedures
For further study.
4. Network capabilities for charging
This Recommendation does not cover charging principles. Future Recommendations in the D-Series are
expected to contain that information. It shall be possible to charge the subscriber accurately for the service.
5. Interworking requirements
For further study.
6. Interaction with supplementary services
For further study.
7.1 Attributes/values
a) Low layer attributes
Information transfer attributes
Videotex centre to
User to Videotex|Videotex centre,
centre|external computers
ûûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûû
1. Mode:Circuit (Note 1)| Circuit/packet
2. Rate:64 kbit/s | FS
3. Info transfer cap.:unrestricted | FS
4. Structure:FS | FS
5. Establishment:Demand | Demand/permanent
6. Configuration:Point-to-point | Point-to-point,
| multipoint
|
7. Symmetry:Bidirectional | Bidirectional
symmetric | symmetric
Access attributes
8. Access channel: B for user info (Note 2), D for signalling
9. Signalling a.p. layer 1: I.430/I.431
9.1 Signalling a.p. layer 2: I.440/I.441
9.2 Signalling a.p. layer 3: I.450/I.451
9.3 Information a.p. layer 1: I.430/I.431
9.4 Information a.p. layer 2: X.75 (SLP)
9.5 Information a.p. layer 3: ISO 8208
b) High layer attributes
10. Type of user info: Videotex
11. Layer 4 protocol:
12. Layer 5 protocol:
13. Layer 6 protocol: FS
13.1 Resolution [ppi]:
13.2 Graphic mode:
14. Layer 7 protocol:
c) General attributes: FS
Note 1 - The use of packet mode is for further study.
Note 2 - The use of the D Channel for Videotex information is for further study.
7.2 Videotex supported by an ISDN
In the following table the recommended overall support, and recommended support for the variations of the non-
dominant attributes are given. The definition of E(Essential) and A(Additional) can be found in RecommendationI.240.
a) Overall support: A
b) Variations of non-dominant attributes:
b.1)Information transfer mode|Support
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circuit |user terminal-to-Videotex centre |A | |
|videotex centre to Videotex centre, |A |external com-
puter |
| |
packet|Videotex centre to Videotex centre,|A
|external computer |
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| | |
b.2)Establishment |Symmetry|Communication|Support
of communication | |configuration |
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demand |bidirectional|pt-pt|E
permanent (Note 3)|symmetric | | | | |
demand |bidirectional |multipoint|A
permanent (Note 3)|symmetric | (Note 3) |
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b.3)Access:
Signalling & OAM||
(Note 4)|User information|Support
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Channel ||Channel| |
& rate| Protocols|& rate|Protocols|
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Circuit mode | | |
| | |
D(16)| I.430, I.440, I.441|B(64)|I.430|A
| I.450, I.451 (Note 5) | | X.75(SLP), | |||ISO 8208 |
| | | |
D(64)|I.431, I.440, I.441|B(64)|I.431, |
|I.450, I.451 (Note 5) | | X.75(SLP),|A |||ISO 8208 |
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Packet mode | | |
| | |
D(16)|FS|B(64)|FS|FS || or || ||D(16) ||
| | | |
D(64)|FS|B(64)|FS|FS || | |
| | | |
VC in|FS|B(64)|FS|FS
B(64) | | | |
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Note 3 - Between Videotex centres and to external computers.
Note 4 - Definition of protocols for OAM are FFS.
Note 5 - Demand services only. Others are FFS.
8. Dynamic description
The circuit mode dynamic description appears in RecommendationI.220.
I.241.6 Telex
1. Definition
This service provides interactive text communication. The digital signal at the S/T reference point follows the inter-
nationally agreed Recommendations for telex above the ISDN physical layer.
2. Description
For further study.
3. Procedures
For further study.
4. Network capabilities for charging
This Recommendation does not cover charging principles. Future Recommendations in the D-Series are expected to
contain that information. It shall be possible to charge the subscriber accurately for the service.
5. Interworking requirements
For further study.
6. Interaction with supplementary services
For further study.
7. Attributes/values
7.1 a) Low layer attributes
Information transfer attributes
1. Information transfer mode: circuit; packet is FFS (Note 1)
2. Information transfer rate: 64kbit/s
3. Information transfer capabilitiy: unrestricted
4. Structure: 8kHz integrity
5. Establishment of communication: reserved/permanent
6. Communication configuration: point-to-point
7. Symmetry: bidirectional
Access attributes
8. Access channel: B/user information, D/signalling, D/telex user information is FFS (Note 1)
9.1 Signalling a.p. layer 1: I.430/I.431
9.2 Signalling a.p. layer 2: U.202
9.3 Signalling a.p. layer 3: U.202
9.4 Information a.p. layer 1: I.430/I.431
9.5 Information a.p. layer 2: U.202
9.6 Information a.p. layer 3: FS
b) High layer attributes
10. Type of user information: Telex
11. Layer 4 protocol: --
12. Layer 5 protocol: --
13. Layer 6 protocol: --
14. Layer 7 protocol: --
c) General attributes
15. Supplementary services provided: FS
16. Quality of service: FS
17. Interworking possibilities: Telex, Teletex, others: FS
18. Operational and commercial: FS
Note 1 - Subject to satisfying telex quality of service on D-channel.
7.2 Telex supported by an ISDN
In the following table the recommended overall support, and recommended support for the variations of the non-
dominant attributes are given. The definition of E(Essential) and A(Additional) can be found in RecommendationI.240.
a) Overall support: FS
b) Variations of non-dominant attributes:
b.1)Information transfer mode|Support
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circuit|FS
packet|FS
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| | |
b.2)Establishment|Symmetry|Communication|Support
of communication | | |
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demand|bidirectional|pt-pt|E
reserved|symmetric |pt-pt |FS permanent | |pt-pt |A |
| |
demand |bidirectional |multipt|A reserved |symmetric |multipt |FS permanent |
|multipt |A ûûûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûûû+ûûûûûûûûû
b.3)Access:
Signalling & OAM||
(Note 2)|User information|Support
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Channel ||Channel| |
& rate| Protocols|& rate|Protocols|
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Circuit mode | | |
| | |
D(16)| I.430, I.440, I.441|B(64)|I.430|FS | I.450, I.451 (Note 3) | | U.202 | |||(Note
4) |
| | | |
D(64)|I.431, I.440, I.441|B(64)|I.431, |
|I.450, I.451 (Note 3) | | U.202 |FS |||(Note 4) |
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Packet mode | | |
| | |
D(16)|"(Note 1)|D(16)|FS |FS
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Note 2 - Definition of protocols for OAM are FFS.
Note 3 - Layer 2 and 3 protocols are FFS.
Note 4 - Others are FFS.
8. Dynamic description
For further study.
