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.\"                 Not Copyright ( c) 1991 
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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 1P
.ce 1000
\v'3P'
SECTION\ 4
.ce 0
.sp 1P
.ce 1000
\fBTELESERVICES\ SUPPORTED\ BY\ AN\ ISDN\fR 
.ce 0
.sp 1P
.sp 2P
.LP
\fBRecommendation\ I.240\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBDEFINITION\ OF\ TELESERVICES\fR 
.EF '%	Fascicle\ III.7\ \(em\ Rec.\ I.240''
.OF '''Fascicle\ III.7\ \(em\ Rec.\ I.240	%'
.ce 0
.sp 1P
.ce 1000
\fI(Melbourne, 1988)\fR 
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR 	\fBGeneral\fR 
.sp 1P
.RT
.PP
Recommendation I.210 describes the principles for defining
telecommunication services supported by an ISDN, including the concept of
bearer services, bearer capabilities and teleservices.  It also provides the
tools for the definition and description of such services.
.PP
The purpose of this Recommendation is to define a recommended set of teleservices 
to be supported by an ISDN. These definitions form the basis for detailed 
descriptions of teleservices as given in Recommendation\ I.241 which 
are used to define the network capabilities required.
.PP
Teleservices are described by prose definitions and descriptions, by attributes 
and by dynamic descriptions, which altogether define the service 
characteristics at a given access point where the customer accesses the
service. Recommendation\ I.140 and Recommendation\ I.210, Annex\ C describe the
use of attributes for this purpose.
.RT
.sp 2P
.LP
\fB2\fR 	\fBDefinition of teleservices in ISDN\fR 
.sp 1P
.RT
.PP
This section defines the teleservices identified so far to be
supported by an ISDN. Additional teleservices are for further study.
.PP
The definition of teleservices is based upon the list of attributes
given in Recommendation\ I.210, Annex\ C.
.PP
The higher layer attribute values (i.e. the layer 4 to 7 protocol
functions and \*Qtype of user information\*U) the low layer attribute values
(i.e.,\ the information transfer attributes, the access attributes and the
general attributes) are the recommended functions for teleservices. The 
\*Qtype of user information\*U attribute is considered the only dominant 
attribute. The value of this attribute is the same as the service name 
used in the 
E\(hy and F\(hyseries Recommendations for the particular service being 
provided in 
ISDN.
.PP
The information transfer and access attribute values for teleservices given 
in the service descriptions are the proposed values when using the 
circuit\(hymode and packet\(hymode bearer capabilities of the ISDN. For 
the case of telephony, only the circuit\(hymode is to be used. Implementations 
using 
alternative low layer attribute values are permitted but are for further 
study. From a service interworking perspective it is desirable that the 
possible 
combinations of values of the low layer attributes of teleservices be the 
same as the bearer capabilities of the bearer services defined in I.230\(hyseries 
of 
Recommendations.
.bp
.PP
The following teleservices have been identified so far to be supported 
by an ISDN: 
.RT
.LP
	I.241.1
	Telephony
.LP
	I.241.2
	Teletex
.LP
	I.241.3
	Telefax 4
.LP
	I.241.4
	Mixed mode
.LP
	I.241.5
	Videotex
.LP
	I.241.6
	Telex
.PP
The prose descriptions (step 1.1) and static descriptions (step
1.2) of these services are given in Recommendation\ I.241. The common dynamic
description (step 1.3) for demand bearer services given in Recommendation\ 
I.220 is also applicable to teleservices. 
.PP
\fINote\fR \ \(em\ Prose descriptions for mixed mode, Videotex and telex 
are not yet included. 
.RT
.sp 2P
.LP
\fB3\fR 	\fBRecommended support of teleservices\fR 
.sp 1P
.RT
.PP
In order to facilitate the development of compatible ISDNs and
related user equipment, Recommendation\ I.241 outlines the recommended 
support of teleservices defined in this Recommendation. This outline consists 
of two 
parts:
.RT
.LP
	a)
	 description of the overall support of a teleservice by its dominant attribute 
value, i.e.,\ the value of the high layer attribute: type of user information. 
The recommended overall support of a teleservice is described as: 
.LP
	E
	an essential teleservice to be made available
internationally;
.LP
	A
	an additional teleservice which may be available in
some ISDNs, and which may also be available internationally;
.LP
	FS
	the recommended support of this teleservice is for
further study,
.LP
	b)
	with each teleservice, a description of the agreed
non\(hydominant attributes, e.g.\ values of the high layer attributes: 
layer\ 4 to\ 7 protocol functions. If an ISDN supports the teleservice, 
the recommended 
support of the values of these secondary attribute combinations within this
teleservice is described as:
.LP
	E
	 an essential combination of attribute values to be made available internationally 
(when an ISDN supports the particular teleservice); 
.LP
	A
	 an additional combination of attribute values which may be available 
in some ISDNs, and which may also be available internationally 
(when an ISDN supports the particular teleservice);
.LP
	FS
	the recommended support of this combination of
attributes is for further study.
.PP
\fINote\fR \ \(em\ During an evolutionary period, not all items marked 
\*QE\*U will be provided in all networks. 
.PP
The recommended overall support of teleservices as given in
Recommendation\ I.241 is summarized in Table\ 1/I.240.
.RT
.sp 2P
.LP
\fB4\fR 	\fBProse definitions of teleservices\fR 
.sp 1P
.RT
.PP
In order to give an overview of the teleservices identified, their definitions, 
as given in Recommendation\ I.241, are reproduced below. 
.RT
.sp 1P
.LP
I.241.1
	\fBTelephony\fR 
.sp 9p
.RT
.PP
The \*Qtelephony service\*U provides users with the ability for
real\(hytime two\(hyway speech conversation via the network.
.RT
.sp 1P
.LP
I.241.2
	\fBTeletex\fR 
.sp 9p
.RT
.PP
Teletex is an international service enabling subscribers to
exchange office correspondence in the form of documents containing Teletex
coded information on an automatic memory\(hyto\(hymemory basis via the ISDN.
.RT
.sp 1P
.LP
I.241.3
	\fBTelefax 4\fR 
.sp 9p
.RT
.PP
Telefax 4 is an international service enabling subscribers to
exchange office correspondence in the form of documents containing facsimile
coded information automatically via the ISDN.
.bp
.RT
.ce
\fBH.T. [T1.240]\fR 
.ce
TABLE\ 1/I.240
.ce
\fBRecommended overall support of teleservices by ISDNs\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(36p) | cw(48p) | cw(36p) .
No.	Service	Support
_
.T&
cw(36p) | lw(48p) | lw(36p) .
I.241.1	Telephony	E/A | ua\d\u)\d
.T&
cw(36p) | lw(48p) | lw(36p) .
I.241.2	Teletex	A
.T&
cw(36p) | lw(48p) | lw(36p) .
I.241.3	Telefax 4	A
.T&
cw(36p) | lw(48p) | lw(36p) .
I.241.4	Mixed mode	A
.T&
cw(36p) | lw(48p) | lw(36p) .
I.241.5	Videotex	A
.T&
cw(36p) | lw(48p) | lw(36p) .
I.241.6	Telex	FS
.TE
.LP
\ua\d\u)\d
It is anticipated that ISDNs will 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.
.nr PS 9
.RT
.ad r
\fBTableau 1/I.240 [T1.240], p.1\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
I.241.4
	\fBMixed mode\fR 
.sp 9p
.RT
.PP
This service provides combined text and facsimile communication
(mixed mode) for end\(hyto\(hyend transfer of documents containing mixed 
information of text and fixed images. The high layer attributes are based 
on the 
Recommendations for Teletex and Telefax\ 4.
.RT
.sp 1P
.LP
I.241.5
	\fBVideotex\fR 
.sp 9p
.RT
.PP
The Videotex service in the ISDN is an enhancement of the existing Videotex 
service with retrieval and mailbox functions for text (alpha) and 
graphic information.
.RT
.sp 1P
.LP
I.241.6
	\fBTelex\fR 
.sp 9p
.RT
.PP
This service provides interactive text communication. The digital signal 
at the SB/FT reference point follows the internationally agreed 
Recommendations for telex above the ISDN physical layer.
.RT
.sp 2P
.LP
\fBRecommendation\ I.241\fR 
.RT
.sp 2P
.sp 1P
.ce 1000
\fBTELESERVICES\ SUPPORTED\ BY\ AN\ ISDN\fR 
.EF '%	Fascicle\ III.7\ \(em\ Rec.\ I.241''
.OF '''Fascicle\ III.7\ \(em\ Rec.\ I.241	%'
.ce 0
.sp 1P
.ce 1000
\fI(Melbourne, 1988)\fR 
.sp 9p
.RT
.ce 0
.sp 1P
.PP
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. 
.sp 1P
.RT
.PP
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. 
.PP
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 service description method. 
.PP
The recommended support for these teleservices is given in \(sc\ . |  | 8
(i.e.\ 1.8, 2.8, 3.8\ etc.)  of each individual service description.
.bp
.RT
.sp 2P
.LP
\fB1\fR 	I.241.1\ \(em
	\fBTelephony\fR 
.sp 1P
.RT
.sp 1P
.LP
1.1
	\fIDefinition\fR 
.sp 9p
.RT
.PP
The \*Qtelephony service\*U provides users with the ability for
real\(hytime two\(hyway speech conversation via the network.
.RT
.sp 2P
.LP
1.2
	\fIDescription\fR 
.sp 1P
.RT
.sp 1P
.LP
1.2.1
	\fIGeneral description\fR 
.sp 9p
.RT
.PP
The \*Qtelephony service\*U provides speech transmission at an audio
bandwidth of 3.1\ kHz. The communication is bidirectional, 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\(hyrate encoding. 
.PP
The digital signal at the SB/FT reference point follows the encoding
laws for speech (according to Recommendation G.711), A\(hylaw or \(*m\(hylaw 
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\(hychannel, 
signalling is provided over the D\(hychannel. Tones and announcements are 
provided by the network, encoded according to Recommendation G.711, although 
terminals can generate tones or other indications based on the messages 
received. 
.RT
.sp 1P
.LP
1.2.2
	\fISpecific terminology\fR 
.sp 9p
.RT
.LP
	a)
	\fIVoice quality\fR \ \(em\ The required acoustic performance
is described in terms of loudness ratings, frequency response,
quantizing distortion,\ etc. Overall requirements are given in
the Recommendations of the P\(hySeries.
.LP
	b)
	\fITransmission delay\fR \ \(em\ The maximum delay is that
specified for the general telephone network
(cf.\ Recommendation\ G.114). The permissible variation of the
actual delay is for further study.
.LP
	c)
	\fIRetention timer\fR \ \(em\ This timer specifies the amount
of time that the network retains the call information of the
original call upon encountering busy or being released. It
is a network provider option. The value for this timer is
greater than 15\ seconds.
.sp 2P
.LP
1.3
	\fIProcedures\fR 
.sp 1P
.RT
.sp 1P
.LP
1.3.1
	\fIProvisionB/Fwithdrawal\fR 
.sp 9p
.RT
.PP
1.3.1.1
Provision of this service will be by pre\(hyarrangement with
the Administration.
.sp 9p
.RT
.PP
1.3.1.2
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:
.LP
.sp 1
\fISubscription Option\fR \fIValue\fR Maximum number of information channels 
available at user B 
\(em\ 
	\fIm\fR , where \fIm\fR  | is not greater than the number of information
channels on the interface
	Maximum number of total calls present at user B
\(em
	\fIn\fR , where \fIn\fR  | is not greater than the number of information
channels on the interface
	
.bp
.PP
User B can be an ISDN number or group of ISDN numbers on the
interface.
.PP
\fINote\fR \ \(em\ More than one ISDN number can be associated with the
serviceB/Finterface 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 network
provider option, separate values may be specified for incoming and for 
outgoing calls for either or both of the limits. 
.RT
.sp 1P
.LP
1.3.2
	\fINormal procedures\fR 
.sp 9p
.RT
.LP
	a)
	\fIOriginating the service (call set\(hyup)\fR 
.LP
	 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.
.LP
	i)
	A service selection is required on a multi\(hyservice
terminal.
.LP
	ii)
	Terminating customer selection is selecting the
required  termination (user/network interface) by an
appropriate  means [for example, the use of
direct\(hydialling\(hyin (DDI), or multiple subscriber
number].
.LP
	iii)
	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 audible indications
which may be accompanied by other indications.
.LP
	b)
	\fICall acceptance (answer)\fR 
.LP
	Selection of the terminating customer is indicated to each
user by appropriate indications (
\fIcall arrival\fR \fIindication\fR and 
\fIawaiting answer indication\fR ). 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 \*Qspeech phase\*U.
.LP
	c)
	\fICall release\fR 
.LP
	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.
.LP
	d)
	\fIFailure situations due to user error\fR 
.LP
	The following failure situations may occur due to user
error:
.LP
	i)
	user taking too long to input the network address
information will be given a failure indication,
e.g.\ during overlap sending (see Recommendations\ I.451
and\ I.220);
.LP
	ii)
	user inputting a non valid network address, e.g.\ an
unallocated address, will be given a failure indication.
.LP
	e)
	\fIFailure indications due to terminating termination\fR 
\fIstate\fR 
.LP
	i)
	User attempting to set up a call to a termination
where no free B\(hychannels are available will receive a busy
indication unless call waiting or another supplementary
service is in operation.
.LP
	\fINote\fR \ \(em\ 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.
.LP
	ii)
	User attempting to set up a call to a termination
where the call is not accepted, i.e.\ no response
indicating call acceptance is received, will, after a
defined period, be given a call failure indication (see
Recommendations\ I.451 and\ I.220).
.LP
	f
)
	\fIFailure situations due to network conditions\fR 
.LP
	User attempting to set up a call but meeting problems in
the network (e.g.\ congestion) will be given a suitable
indication.
.bp
.sp 1P
.LP
1.4
	\fINetwork capabilities for charging\fR 
.sp 9p
.RT
.PP
This Recommendation does not cover charging principles. Future
Recommendations in the D\(hySeries are expected to contain that information.
.PP
It shall be possible to charge the subscriber accurately for the
service.
.RT
.sp 2P
.LP
1.5
	\fIInterworking requirements\fR 
.sp 1P
.RT
.PP
1.5.1
Interworking is required between the ISDN and PSTN.
.sp 9p
.RT
.sp 1P
.LP
1.6
	\fIInteraction with supplementary services\fR 
.sp 9p
.RT
.PP
Not applicable. Each supplementary service description identifies the applicability 
with this teleservice. 
.RT
.sp 2P
.LP
1.7
	\fIAttributes and values of attributes of the telephony service\fR 
.sp 1P
.RT
.sp 1P
.LP
	a)
	\fILOW\ LAYER\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	\fIInformation transfer attributes\fR 
.LP
	1.
	Information\ transfer\ mode:
	circuit
.LP
	2.
	Information\ transfer\ rate:
	64 kbit/s
.LP
\fR 	3.
	Information\ transfer\ capability:
	speech
.LP
\fR 	4.
	Structure:
	8 kHz integrity
.LP
\fR 	5.
	Establishment\ of\ communication:
	on demand
.LP
\fR 	6.
	Symmetry:
	bidirectional symmetric
.LP
\fR 	7.
	Communication\ configuration:
	point\(hyto\(hypoint
.LP
\fR 	\fIAccess attributes\fR 
.LP
	8.
	Access\ channel\ (and\ rate):
	B(64) for user information,
D\ for signalling (Note)
.LP
	9.
	Access protocol
.LP
	9.1
	Signalling\ access\ protocol\ layer\ 1:
	I.430/I.431
.LP
	9.2
	Information\ access\ protocol\ layer\ 2:
	I.440/I.441
.LP
	9.3
	Signalling\ access\ protocol\ layer\ 3:
	I.450/I.451
.LP
	9.4
	Information\ access\ protocol\ layer\ 1:
	I.430/I.431; G.711
.LP
	9.5
	Signalling\ access\ protocol\ layer 2:
	not applicable
.LP
	9.6
	Information\ access\ protocol\ layer\ 3:
	not applicable
.sp 1P
.LP
	b)
	\fIHIGH\ LAYER\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	10.
	Type\ of\ user\ information:
	speech
.LP
	11.
	Layer\ 4\ protocol\ functions:
	not applicable
.LP
	12.
	Layer\ 5\ protocol\ functions:
	not applicable
.LP
	13.
	Layer\ 6\ protocol\ functions:
	Recommendation G.711
.LP
	14.
	Layer\ 7\ protocol\ functions:
	not applicable
.sp 1P
.LP
	c)
	\fIGENERAL\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	15.
	Supplementary\ services\ provided:
	further study
.LP
	16.
	Quality\ of\ Service:
	further study
.LP
	17.
	Interworking\ possibilities:
	to and from PSTN
.LP
	18.
	Operational\ and\ commercial:
	further study
.PP
\fR \fINote\fR \ \(em\ For reserved/permanent services, the operational,
administrative and maintenance messages (OAM) related to these services 
may be conveyed over the D\(hychannel. 
.sp 1P
.LP
1.8
	\fIRecommended support of telephony by an ISDN\fR 
.sp 9p
.RT
.LP
The definition of E (essential) and A (additional) can be found in Recommendation\ 
I.240. 
.FE
	a)
	Overall support
: E/A
.LP
	 \fINote\fR \ \(em\ It is anticipated that ISDNs will 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. 
.bp
.LP
	b)
	Variations of non\(hydominant attributes :
.LP
	1)
	Information transfer mode
.LP
	\(em
	Circuit : E
.sp 2P
.LP
	2)
	\fIEstablishment\fR 	\fISymmetry\fR 	\fICommunication\fR 	\fISupport\fR 
	\fIof communication\fR 	\fIconfiguration\fR 	\fIsupport\fR 
.sp 1P
.RT
.sp 1P
.LP
	demand
		pt\(hypt
	E
.sp 9p
.RT
.LP
		reserved
		bidirectional
	pt\(hypt
	FS
.LP
	
	permanent
		sym\*'etrique
	pt\(hypt
	A
		demand
		multipt
	A
.LP
		reserved
		bidirectional
	pt\(hypt
	FS
.LP
	
	permanent
		sym\*'etrique
	multipt
	A
.sp 1P
.LP
	3)
	Access
.sp 9p
.RT
.LP
.sp 2
.ce
\fBH.T. [T1.241]\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) sw(48p) | cw(48p) sw(48p) | cw(36p) , c | c | c | c | ^ .
Signalling and OAM (Note 1)	User information	Support
Channel and rate	Protocols	Channel and rate	Protocols
_
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(16)	 {
I.430, I.440, I.441, I.450, I.451
(Note\ 2)
 }	B(64)	I.430, G.711	E
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(64)	 {
I.431, I.440, I.441, I.450, I.451
(Note\ 2)
 }	B(64)	I.431, G.711	E
.LP
\fINote\ 1\fR
\ \(em\ Definition of protocols for OAM is for further study.
.LP
\fINote\ 2\fR
\ \(em\ Demand services only. Others are for further study.
.nr PS 9
.RT
.ad r
\fBTable [T1.241], p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
.sp 2
1.9
	\fIDynamic description\fR 
.sp 9p
.RT
.PP
The circuit\(hymode dynamic description appears in
Recommendation\ I.220.
.RT
.sp 2P
.LP
\fB2\fR 	I.241.2\ \(em
	\fBTeletex\fR 
.sp 1P
.RT
.PP
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 
step\ 1.1 of the service description method. Further alignment with this
description method requires further study.
.RT
.LP
.sp 1
.bp
.sp 1P
.LP
2.1
	\fIDefinition\fR 
.sp 9p
.RT
.PP
Teletex is an international service, enabling subscribers to
exchange office correspondence in the form of documents containing Teletex
coded information on an automatic memory\(hyto\(hymemory basis via the ISDN.
.RT
.sp 2P
.LP
2.2
	\fIDescription\fR 
.sp 1P
.RT
.sp 1P
.LP
2.2.1
	\fIScope\fR 
.sp 9p
.RT
.PP
The Teletex service provides communication between Teletex
equipment
.FS
Teletex equipment may be a Teletex terminal or a system.
.FE
which are used for the preparation, editing and printing of correspondence
containing text information using a standardized character set
(see Recommendation\ T.61).
.PP
The basic element of the correspondence between users is the page
which is the smallest unit of text treated as an entity. No restrictions 
shall exist concerning the operator procedures for generation of the text 
or the 
positioning of text within the printable area on a page.
.PP
\fINote 1\fR \ \(em\ 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.
.PP
\fINote 2\fR \ \(em\ 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.
.PP
\fINote 3\fR \ \(em\ 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 Recommendation F.220.
.RT
.sp 2P
.LP
2.2
	\fIOperation\fR 
.sp 1P
.RT
.sp 1P
.LP
2.2.2.1
	\fIGeneral\fR 
.sp 9p
.RT
.PP
The Teletex service in each country and the international
interconnection between countries or networks shall use automatic switching 
so that it is possible for any Teletex subscriber to reach any other Teletex 
subscriber using fully automatic selection.
.PP
It is a requirement to allow the through\(hyconnection of a call
between a Teletex terminal connected to a private automatic branch exchange 
(or similar systems) and those connected to public exchanges used for the 
Teletex service. 
.PP
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. 
.PP
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, allowing both communications between persons and data 
base access (see Recommendation I.210). 
.PP
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 (see 
Recommendation\ F.220).
.PP
Mixed mode
of operation using the techniques of Telefax 4 for the transfer of facsimile\(hycoded 
information and of Teletex for the transfer of character\(hycoded text 
is described as a standardized option within the Teletex service in Recommendation 
F.230. 
.PP
Two\(hyway alternate (TWA) communication is a capability of the Teletex 
service, which also includes one\(hyway communication (OWC); the calling 
subscriber will have full control of the Teletex call.
.RT
.LP
.sp 1
.bp
.sp 2P
.LP
2.3
	\fIProcedures\fR 
.sp 1P
.RT
.sp 1P
.LP
2.3.1
	\fIProvisionB/Fwithdrawal\fR 
.sp 9p
.RT
.PP
The national and international facilities of the Teletex service, including 
the TeletexB/Ftelex conversion facilities, shall be open 
continuously.
.PP
Teletex subscriber equipment for which call numbers are published
in the directories shall, in principle, be available to accept calls
continuously.
.PP
In order to facilitate the 24\(hyhour duration of the service, it is
permitted to use a centralized storage in the network to realize the receiving 
memory capability of the terminal. 
.RT
.sp 1P
.LP
2.3.2
	\fICall phases\fR 
.sp 9p
.RT
.PP
The operations for each call may be divided into the following
three phases:
.RT
.LP
	a)
	Preparation
.LP
	\(em
	preparation of the information in local mode;
.LP
	\(em
	loading of the information into a memory,
.LP
	b)
	Transmission (in principle, automatic)
.LP
	\(em
	call establishment;
.LP
	\(em
	pre\(hyinformation phase (see Note);
.LP
	\(em
	information transfer from memory\(hyto\(hymemory (see
Note);
.LP
	\(em
	post information phase (see Note);
.LP
	\(em
	call clearing.
.LP
	\fINote\fR \ \(em\ During these parts of the transmission phase the
network must be transparent with respect to control procedures.
.LP
	c)
	Output
.LP
	\(em
	emptying the memory.
.PP
\fINote\fR \ \(em\ The information may consist of one or more Teletex
documents each consisting of one or more Teletex pages.
.PP
The control procedures as specified in Recommendation T.62 shall
be used as end\(hyto\(hyend communication procedures between any Teletex 
equipment in the basic service. 
.PP
The lower layer protocols and the network independent basic transport protocol 
to be used for Teletex are specified in Recommendations\ T.70 
and\ T.90.
.PP
The network\(hydependent control procedures for the Teletex are those
that are defined for ISDN.
.RT
.sp 1P
.LP
2.3.3
	\fICall identification line\fR 
.sp 9p
.RT
.PP
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
purposes.
.PP
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.
.PP
The call identification line is composed of four fields as follows\fR (see 
Figure\ 1/I.241): 
.RT
.LP
	\(em
	Field\ 1:
	identification of the called Teletex
equipment
;
.LP
	\(em
	Field\ 2:
	identification of the calling Teletex
equipment
;
.LP
	\(em
	Field\ 3:
	date and time;
.LP
	\(em
	Field\ 4:
	supplementary reference information.
.bp
.LP
.rs
.sp 23P
.ad r
\fBFigure 1/I.241 [T2.241], p. (\*`a traiter comme tableau MEP)\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
2.3.4
	\fIError protection\fR 
.sp 9p
.RT
.PP
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. 
.PP
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\(hyinformation, information and post\(hyinformation 
phases should not exceed 1 in 10\u6\d characters. 
.RT
.sp 1P
.LP
2.4
	\fINetwork capabilities for charging\fR 
.sp 9p
.RT
.PP
This Recommendation does not cover charging principles. Future
Recommendations in the D\(hySeries are expected to contain that information.
.PP
It shall be possible to charge the subscriber accurately for the
service.
.RT
.sp 2P
.LP
2.5
	\fIInterworking requirements\fR 
.sp 1P
.RT
.PP
2.5.1
Within the Teletex service, interworking between terminals
connected to different networks is required. Real\(hytime connection between
terminals operating at different speeds has to be provided on the basis 
of at least 2.4\ kbitB/Fs. 
.sp 9p
.RT
.sp 2P
.LP
2.5.2
	\fIIntercommunication with other services\fR 
.sp 1P
.RT
.PP
2.5.2.1
The Teletex service will provide the ability for
intercommunication in both directions with the telex service by means of
conversion facilities (see Recommendations\ F.201, U.201, T.390).
.bp
.sp 9p
.RT
.PP
2.5.2.2
Intercommunication between basic mode and mixed mode Teletex
terminals and Classes\ I, II and III Group\ 4 facsimile terminals is shown in
Table\ 1/I.241 (see Recommendation F.184).
.PP
2.5.2.3
The Teletex service allows for intercommunication with telex and
with the  Interpersonal Messaging Service (IPM) (see
Recommendations\ F.421, F.422).
.ce
\fBH.T. [T3.241]\fR 
.ce
TABLE\ 1/I.241
.ce
\fBCurrent status of direct intercommunication\fR 
.ce

.ce
\fBfor Teletex and Group 4 facsimile terminals on the same network\fR 
.ce

.T&
lw(48p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) .
						
.T&
lw(48p) | cw(30p) | cw(30p) | cw(30p) | lw(30p) | lw(30p) | lw(30p) .
Facsimile Group 4, Class\ I	F	F	F			
_
.T&
lw(48p) | cw(30p) | cw(30p) | cw(30p) | lw(30p) | lw(30p) | lw(30p) .
Facsimile Group 4, Class\ II	F	F	F			
_
.T&
lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Facsimile Group 4, Class\ III	F	T, F, MM	T, F, MM	T	T, MM	T
_
.T&
lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Teletex basic mode		T	T	T	T	T
_
.T&
lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Teletex mixed mode		T, MM	T, MM	T	T, MM	T
_
.T&
lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Teletex processable mode\ 1		T	T	T	T	T, PM1
.TE
.IP T:
Basic Teletex document with character coded information only.
.IP F:
Group 4 facsimile document with facsimile coded information only.
.IP MM:
Mixed\(hymode document with character and facsimile coded information.
.IP PM1:
Processable mode document with character coded information only.
.nr PS 9
.RT
.ad r
\fBTable 1/I.241 [T3.241], p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
2.6
	\fIInteraction with supplementary services\fR 
.sp 9p
.RT
.PP
Each supplementary service description identifies the applicability with 
this teleservice. 
.PP
For the ISDN, the international supplementary services which may be
used for Teletex in the circuit mode using a B\(hyChannel are:
.RT
.LP
	i)
	closed user group;
.LP
	ii)
	multiple subscriber number;
.LP
	iii)
	user\(hyto\(hyuser signalling;
.LP
	iv)
	calling line identification presentation;
.LP
	v)
	calling line identification restriction;
.LP
	vi)
	connected line identification presentation;
.LP
	vii)
	connected line identification restriction;
.LP
	viii)
	direct\(hydialling\(hyin.
.PP
The use of other supplementary services is for further study.
.PP
Supplementary services for Teletex with a packet\(hymode of operation are 
for further study. 
.bp
.RT
.sp 2P
.LP
2.7
	\fIAttributes and values of attributes of the Teletex service\fR 
.sp 1P
.RT
.sp 1P
.LP
	a)
	\fILOW\ LAYER\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	\fIInformation transfer attributes\fR 
.LP
.sp 1
\fICircuit\(hymode bearer capability\fR \fIPacket\(hymode bearer capability\fR 
1. 
Information transfer mode
circuit
packet
2.
Information transfer 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
.LP
3.
Information transfer capability
unrestricted (Note 1)
unrestricted
4.
Structure
unstructured (Note 2)
service data unit integrity
5.
Establishment of communication
demand
demand (VC), permanent (PVC)
.LP
6.
Symmetry
bidirectional symmetric
bidirectional symmetric
7.
Communication configuration
point\(hyto\(hypoint
point\(hyto\(hypoint 
.rs
.sp 20P
.ad r
\fBblanc\fR 
.ad b
.RT
.LP
.bp
.LP
	\fIAccess attributes\fR 
.LP
.sp 1
\fICircuit\(hymode bearer capability\fR \fIPacket\(hymode bearer capability\fR 
8. 
Access channel:
B for user information
D for signalling
user information over virtual circuit within B\(hy or D\(hychannel. When
D\(hychannel is used, maximum packet size and quality of service may be
restricted. Signalling may be provided via D\(hychannel and/or virtual
circuit within B\(hychannel.
.LP
9.
Access protocol
9.1
Signalling access protocol
layer 1:
Rec. I.430/I.431
Rec. I.430/I.431
9.2
Signalling access protocol
layer 2:
Rec. I.440/I.441
Rec. I.440/I.441, X.31
9.3
Signalling access protocol
layer 3:
Rec. I.450/I.451
Rec. I.450/I.451, X.31
.LP
9.4
Information access protocol
layer 1:
Rec. I.430/I.431
Rec. I.430/I.431
9.5
Information access protocol
layer 2:
Rec. X.75 (SLP)
Rec. X.25 (LAPB)
9.6
Information access protocol
layer 3:
ISO 8208
Rec. X.25 (PLP)
.rs
.sp 20P
.ad r
\fBblanc\fR 
.ad b
.RT
.LP
.bp
.sp 1P
.LP
	b)
	\fIHIGH\ LAYER\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	10.
	Type\ of\ user\ information\ \ :
	Teletex
.LP
	11.
	Layer\ 4\ protocol\ functions:
	T.70
.LP
\fR 	12.
	Layer\ 5\ protocol\ functions:
	T.62
.LP
\fR 	13.
	Layer\ 6\ protocol\ functions:
	T.61
.LP
\fR 	14.
	Layer\ 7\ protocol\ functions:
	T.60
.sp 1P
.LP
	c)
	\fIGENERAL\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	15.
	Supplementary\ services\ provided:
	see \(sc\ 2.6
.LP
	16.
	Quality\ of\ service:
	for further study
.LP
	17.
	Interworking\ possibilities:
	see \(sc\ 2.5
.LP
	18.
	Operational\ and\ commercial:
	for further study
.LP
	SLP
	\(em
	Single link protocol
.LP
	PLP
	\(em
	Packet layer protocol
.LP
	VC
	\(em
	Virtual circuit
.LP
	PVC
	\(em
	Permanent virtual cirtcuit
.PP
\fINote 1\fR \ \(em\ The interworking arrangements with networks having a
restricted 64\ kbit/s information transfer capability require further study.
.PP
\fINote 2\fR \ \(em\ Even if no structure is required the network may provide
8\ kHz integrity.
.RT
.sp 1P
.LP
2.8
	\fIRecommended support of Teletex by an ISDN\fR 
.sp 9p
.RT
.LP
	a)
	Overall support
: A
.LP
	b)
	Variations of non\(hydominant attributes:
.LP
	1)
	Information transfer mode
.LP
	\fINote\fR \ \(em\ In the interim period, the circuit mode
method of operation is preferred
.LP
	\(em
	circuit: A
.LP
	\(em
	packet: A
.sp 2P
.LP
	2)
	\fIEstablishment\fR 	\fISymmetry\fR 	\fICommunication\fR 	\fISupport\fR 
	\fIof communication\fR 	\fIconfiguration\fR 	\fISupport\fR 
.sp 1P
.RT
.sp 1P
.LP
	demand
	bidirectional
	pt\(hypt
	E
.sp 9p
.RT
.LP
		symmeric 
.LP
.sp 15
.bp
.sp 1P
.LP
	3)
	\fIAccess\fR 
.sp 9p
.RT
.ce
\fBH.T. [T4.241]\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) sw(48p) | cw(48p) sw(48p) | cw(36p) , c | c | c | c | ^ .
Signalling and OAM (Note 1)	User information	Support
Channel and rate	Protocols	Channel and rate	Protocols
_
.T&
cw(228p) .
Circuit mode
_
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(16)  	 {
I.430, I.440, I.441, I.450, I.451
(Note\ 2)
 }	B(64)  	I.430,  X.75 (SLP),  ISO 8208	A
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(64)  	 {
I.431, I.440, I.441, I.450, I.451
(Note\ 2)
 }	B(64)  	I.431,  X.75 (SLP),  ISO 8208	A
_
.T&
cw(228p) .
Packet mode
_
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(16)	 {
I.430, I.440, I.441, I.450, I.451, X.31
 }	B(64) or D(16)	 {
I.430,
X.25 LAPB,
X.25 (PLP)
 }	A
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(64)	 {
I.431, I.440, I.441, I.450, I.451, X.31
 }	B(64)	 {
I.431,
X.25 LAPB,
X.25 (PLP)
 }	FS
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
VC in B(64)	for futher study	B(64)	for futher study	FS
.TE
.LP
\fINote\ 1\fR
\ \(em\ Definition of protocols for OAM is for further study.
.LP
\fINote\ 2\fR
\ \(em\ Demand services only. Others are for further study.
.nr PS 9
.RT
.ad r
\fBTableau [T4.241], p.5\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
2.9
	\fIDynamic description\fR 
.sp 9p
.RT
.PP
The circuit\(hymode dynamic description appears in
Recommendation\ I.220.
.RT
.sp 2P
.LP
\fB3\fR 	I.241.3\ \(em
	\fBTelefax\ 4\fR 
.sp 1P
.RT
.PP
The prose description of the Telefax\ 4 service is an extract of
Recommendation\ F.I84. (If more detail is required this Recommendation 
should be referred to.) Therefore it does not strictly follow Step\ 1.1 
of the service 
description method. Closer alignment with the method requires further
study.
.RT
.sp 1P
.LP
3.1
	\fIDefinition\fR 
.sp 9p
.RT
.PP
Telefax 4 is an international service enabling subscribers to
exchange office correspondence in the form of documents containing facsimile
coded information, automatically via the ISDN.
.RT
.sp 2P
.LP
3.2
	\fIDescription\fR 
.sp 1P
.RT
.sp 1P
.LP
3.2.1
	\fIGeneral description\fR 
.sp 9p
.RT
.PP
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 64\ kbitB/Fs digital signals
over the B\(hychannel.
.bp
.PP
There are three classes of Group\ 4 facsimile terminals:
.RT
.LP
	Class\ I
	\(em
	 In this class the minimum requirement terminal is a terminal able to 
send and receive documents containing facsimile encoded information (in 
accordance with Recommendation\ T.6 and the T.400\(hySeries). 
.LP
	Class\ II
	\(em
	 In this class the minimum requirement terminal is a terminal able to 
transmit documents that are facsimile encoded (in 
accordance with Recommendation\ T.6 and the T.400\(hySeries). In addition, the
terminal must be capable of receiving documents which are facsimile coded 
(in accordance with Recommendation\ T.6 and the T.400\(hySeries), teletex 
coded (in 
accordance with the basic coded character repertoire as defined in
Recommendation\ T.61) and also mixed\(hymode documents (in accordance with
Recommendations\ of the T.400\(hySeries).
.LP
	Class\ III
	\(em
	 In this class the minimum requirement terminal is a terminal that is 
capable of generating, transmitting and receiving 
facsimile coded documents (in accordance with Recommendation\ T.6 and
the T.400\(hySeries), teletex coded documents (in accordance with the basic 
coded character repertoire as defined in Recommendation\ T.61) and mixed\(hymode 
documents (in accordance with Recommendations\ of the T.400\(hySeries).
.PP
The basic element of the correspondence between users
is the page which is the smallest unit of text treated as an entity. No
restrictions shall exist concerning the operator procedures for generation 
of the text or the positioning of text within the reproducible area on 
a page. 
.sp 1P
.LP
3.2.2
	\fIOperation\ \(em\ General\fR 
.sp 9p
.RT
.PP
The Telefax\ 4 service in each country and the interconnection
between countries or networks shall use automatic switching so that it is
possible for any Telefax\ 4 subscriber to reach any other Telefax\ 4 subscriber 
using fully automatic selection. 
.PP
It is a requirement to allow the through\(hyconnection of a call between 
Group\ 4 facsimile terminals connected to a private automatic branch exchange 
(or similar systems) and those connected to public exchanges used for the
Group\ 4 facsimile service.
.PP
Two\(hyway alternate (TWA) communication is a capability of the Telefax\ 
4 service, which also includes one\(hyway communication (OWC); the calling 
subscriber will have full control of the Group\ 4 facsimile call.
.RT
.sp 2P
.LP
3.3.
	\fIProcedures\fR 
.sp 1P
.RT
.sp 1P
.LP
3.3.1
	\fIProvisionB/Fwithdrawal\fR 
.sp 9p
.RT
.PP
The national and international Telefax\ 4 service shall be open
continuously.
.PP
Telefax\ 4 terminals for which call numbers are published in the
directories shall, in principle, be available to accept calls continuously.
.PP
In order to facilitate the 24\(hyhour duration of service it is permitted 
to use a centralized storage in the network to realize the receiving memory 
capability of the terminal.
.RT
.sp 1P
.LP
3.3.2
	\fICall phases\fR 
.sp 9p
.RT
.PP
The operations for each call may be divided into the following
three phases:
.RT
.LP
	a)
	preparation:
.LP
	\(em
	preparation of the information to be transmitted;
.LP
	b)
	transmission:
.LP
	\(em
	call establishment (automatic);
.LP
	\(em
	pre\(hyinformation phase (see Note);
.LP
	\(em
	information transfer (see Note);
.LP
	\(em
	post information phase (see Note);
.LP
	\(em
	call clearing.
.LP
	\fINote\fR \ \(em\ During these parts of the transmission phase the
network must be transparent with respect to control procedures.
.bp
.LP
	c)
	output:
.LP
	\(em
	 displaying the message either by immediate printing or from a storage 
medium upon control by the operator. 
.LP
	\fINote\fR \ \(em\ The information may consist of one or more
Telefax\ 4 documents each consisting of one or more Telefax pages.
.PP
The control procedures as specified in Recommendation\ T.62 and
Recommendations of the T.400\(hySeries shall be used as end\(hyto\(hyend 
communication procedures between terminals in the service. 
.PP
The low layer protocols and the network independent basic transport
protocol for Telefax\ 4 are specified in Recommendations T.70 and T.90.
.PP
The network\(hydependent control procedures for the Telefax\ 4 service 
are those that are defined for ISDN. 
.RT
.sp 1P
.LP
3.3.3
	\fICall identification line\fR 
.sp 9p
.RT
.PP
The Telefax\ 4 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
purposes. Date and time have to be provided by the network and sent to the
calling terminal in the call set\(hyup phase.
.PP
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.
.PP
For the format of the call identification line see
Recommendation\ F.200.
.RT
.sp 1P
.LP
3.3.4
	\fIError protection\fR 
.sp 9p
.RT
.PP
To ensure call integrity, error protection will be provided by
Telefax\ 4 control procedures (see Recommendations\ T.62, T.70 and T.90). 
Besides the error detection and correction mechanism in layer 2 (and 3) 
an additional error detection and correction mechanism is provided in the 
session layer. By this mechanism, errors of the higher layer functions 
(e.g.\ commandB/Fresponse 
sequence error) and transmission errors, which are not corrected by the 
lower layers, will be corrected, for example, by retransmission of one 
or several 
pages.
.PP
The error rate on the pre\(hyinformation, information and
post\(hyinformation phases should not exceed 1\ \(mu\ 10\uD\dlF261\u6\d.
.RT
.sp 1P
.LP
3.4
	\fINetwork capabilities for charging\fR 
.sp 9p
.RT
.PP
This Recommendation does not cover charging principles. Future
Recommendations in the D\(hySeries are expected to contain that information.
.PP
It shall be possible to charge the subscriber accurately for the
service.
.RT
.sp 2P
.LP
3.5
	\fIInterworking requirements\fR 
.sp 1P
.RT
.PP
3.5.1
Within the Telefax\ 4 service, interworking between terminals
connected to different networks is required for:
.sp 9p
.RT
.LP
	a)
	Telefax\ 4\ (ISDN)\ \(em\ Telefax\ 4\ (CSPDN:
Circuit switched public data network)
.LP
	b)
	Telefax\ 4\ (ISDN)\ \(em\ Telefax\ 4\ (PSPDN:
Packet switched public data network)
.LP
	c)
	Telefax\ 4\ (ISDN)\ \(em\ Telefax\ 4\ (PSTN:
Public switched telephone network)
.PP
In the case of international interworking between Group\ 4
facsimile terminals connected to dissimilar networks, Recommendation\ X.300
shall apply. For international interworking between PSTN and ISDN, a
(separate) Telefax\ 4 interworking unit may be necessary.
.PP
International routes between ISDNs for the Telefax\ 4 service shall be 
capable of supporting user data rates up to 64\ kbitB/Fs. 
.bp
.RT
.sp 2P
.LP
3.5.2
	\fIIntercommunication with other services\fR 
.sp 1P
.RT
.PP
3.5.2.1
Intercommunication between basic mode and mixed mode
Teletex terminals and Classes\ I, II and III Group\ 4 facsimile terminals
connected to the Telefax\ 4 service is shown in Table\ 2/I.241.
.sp 9p
.RT
.PP
In both the Teletex and Telefax\ 4 services, the equipment
providing mixed mode should enable a direct exchange of documents in accordance 
with Recommendations\ T.6, T.61 and of the T.400\(hySeries. 
.LP
.sp 2
.ce
\fBH.T. [T5.241]\fR 
.ce
TABLE\ 2/I.241
.ce
\fBCurrent status of direct intercommunication\fR 
.ce

.ce
\fBfor Teletex and Group 4 facsimile terminals on the same network\fR 
.ce

.T&
lw(48p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) .
						
.T&
lw(48p) | cw(30p) | cw(30p) | cw(30p) | lw(30p) | lw(30p) | lw(30p) .
Facsimile Group 4, Class\ I	F	F	F			
_
.T&
lw(48p) | cw(30p) | cw(30p) | cw(30p) | lw(30p) | lw(30p) | lw(30p) .
Facsimile Group 4, Class\ II	F	F	F			
_
.T&
lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Facsimile Group 4, Class\ III	F	T, F, MM	T, F, MM	T	T, MM	T
_
.T&
lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Teletex basic mode		T	T	T	T	T
_
.T&
lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Teletex mixed mode		T, MM	T, MM	T	T, MM	T
_
.T&
lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Teletex processable mode\ 1		T	T	T	T	T, PM1
.TE
.IP T:
Basic Teletex document with character coded information only.
.IP F:
Group 4 facsimile document with facsimile coded information only.
.IP MM:
Mixed\(hymode document with character and facsimile coded information.
.IP PM1:
Processable mode document with character coded information only.
.nr PS 9
.RT
.ad r
\fBTable 2/I.241 [T5.241], p. \fR 
.sp 1P
.RT
.ad b
.RT
.PP
.sp 2
3.5.2.2
Intercommunication is desirable between terminals of the
Telefax\ 4 service and terminals of services other than Telefax 4 provided 
over ISDN and other public switched networks. 
.sp 9p
.RT
.PP
Intercommunication possibilities between Telefax\ 4 terminals and Telefax\ 
3 terminals have to be provided (see also Recommendation\ F.180): 
.LP
	a)
	Telefax\ 4\ (ISDN)\ \(em\ Telefax\ 3\ (PSTN)
.LP
	b)
	Telefax\ 4\ (ISDN)\ \(em\ Telefax\ 3\ (ISDN,
via terminal adaptors)
.PP
In case a) Telefax\ 4 terminals use specific service features in
ISDN. Intercommunication should be supported by ISDN\(hyPSTN interworking
units.
.PP
In case b) Telefax\ 3 terminals and Telefax\ 4 terminals which are to be 
connected in the PSTN can also be connected to the ISDN via terminal 
adaptors.
.bp
.RT
.sp 1P
.LP
3.6
	\fIInteraction with supplementary services\fR 
.sp 9p
.RT
.PP
Each supplementary service description identifies the applicability with 
this teleservice. 
.PP
For the ISDN, the international supplementary services for the
Telefax\ 4 service in the circuit mode using a B\(hychannel are:
.RT
.LP
	i)
	closed user group
;
.LP
	ii)
	multiple subscriber number
;
.LP
	iii)
	user\(hyto\(hyuser signalling
;
.LP
	iv)
	calling line identification presentation
;
.LP
	v)
	calling line identification restriction
;
.LP
	vi)
	connected line identification presentation
;
.LP
	vii)
	connected line identification restriction
;
.LP
	viii)
	direct\(hydialling\(hyin
.
.PP
The use of other supplementary services is for further study.
.PP
Supplementary services for Telefax\ 4 with a packet mode of operation are 
for further study. 
.RT
.sp 2P
.LP
3.7
	\fIAttributes and values of attributes of the Telefax\ 4 service\fR 
.sp 1P
.RT
.sp 1P
.LP
	a)
	\fILOW\ LAYER\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	\fIInformation transfer attributes\fR 
.LP
.sp 1
\fICircuit\(hymode bearer capability\fR \fIPacket\(hymode bearer capability\fR 
1. 
Information transfer
mode
circuit
packet
2.
Information transfer
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
.LP
3.
Information transfer capability
unrestricted (Note\ 1)
unrestricted
4.
Structure
unstructured (Note\ 2)
service data unit integrity
5.
Establishment of communication
demand
demand (VC)/permanent (PVC)
.LP
6.
Symmetry
bidirectional symmetric
bidirectional symmetric
7.
Communication configuration
point\(hyto\(hypoint
point\(hyto\(hypoint
.bp
.LP
	\fIAccess attributes\fR 
.LP
.sp 1
\fICircuit\(hymode bearer capability\fR \fIPacket\(hymode bearer capability\fR 
8. 
Access channel
B for user information
D for signalling
User information over virtual circuit within B\(hy or D\(hychannel. When
D\(hychannel is used, maximum packet size and quality of service may be
restricted. Signalling may be provided via D\(hychannel and/or virtual circuit
within B\(hychannel (Note\ 3)
.LP
9.
Access protocol
9.1
Signalling access protocol
layer 1
Rec. I.430/I.431
Rec. I.430/I.431
9.2
Signalling access protocol
layer 2
Rec. I.440/I.441
Rec. I.440/I.441, X.31
9.3
Signalling access protocol
layer 3
Rec. I.450/I.451
Rec. I.450/I.451, X.31
9.4
Information access protocol
layer 1
Rec. I.430/I.431
Rec. I.430/I.431
.LP
9.5
Information access protocol
layer 2
Rec. X.75 (SLP)
Rec. X.25 (LAPB)
9.6
Information access protocol
layer 3
ISO 8208
Rec. X.25 (PLP)
.rs
.sp 20P
.ad r
\fBblanc\fR 
.ad b
.RT
.LP
.bp
.sp 1P
.LP
	b)
	\fIHIGH\ LAYER\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	10.
	Type\ of\ user\ information:
	Telefax 4
.LP
	11.
	Layer\ 4\ protocol\ functions:
	T.70
.LP
	12.
	Layer\ 5\ protocol\ functions:
	T.62
.LP
	13.
	Layer\ 6\ protocol\ functions:
	T.400\(hySeries (Note\ 4)
.LP
	13.1
	Resolution\ [pixels\ per\ inch\ (ppi)]:
	200\ \(mu\ 200 standard;
.LP
240\ \(mu\ 240, 300\ \(mu\ 300, 400\ \(mu\ 400
optional
.LP
	14.
	Layer\ 7\ protocol\ functions:
	T.503, T.521, T.563
.sp 1P
.LP
	c)
	\fIGENERAL\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	15.
	Supplementary\ services\ provided:
	see \(sc\ 3.6
.LP
	16.
	Quality\ of\ service:
	for further study
.LP
	17.
	Interworking\ possibilities:
	see \(sc\ 3.5
.LP
	18.
	Operational\ and\ commercial:
	for further study
.PP
\fINote\ 1\fR \ \(em\ The interworking arrangements with networks having a
restricted 64\ kbitB/Fs information transfer capability require further study.
.PP
\fINote\ 2\fR \ \(em\ Even if no structure is required the network may provide
8\ kHz integrity.
.PP
\fINote\ 3\fR \ \(em\ User information transferred via virtual channel on the
D\(hychannel is for further study.
.PP
\fINote\ 4\fR \ \(em\ Further study is required to identify a more precise
reference in the T.400\(hySeries of Recommendations.
.RT
.sp 1P
.LP
3.8
	\fIRecommended support of Telefax\ 4 by an ISDN\fR 
.sp 9p
.RT
.LP
	a)
	Overall support:
A
.LP
	b)
	Variations of non\(hydominant attributes:
.LP
	1)
	Information transfer mode
.LP
	\fINote\fR \ \(em\ In the interim period, the circuit mode
method of operation is preferred.
.LP
	\(em
	circuit: A
.LP
	\(em
	packet: A
.LP
.sp 1
.sp 2P
.LP
	2)
	\fIEstablishment\fR 	\fISymmetry\fR 	\fICommunication\fR 	\fISupport\fR 
	\fIof communication\fR 	\fIconfiguration\fR 	\fISupport\fR 
.sp 1P
.RT
.sp 1P
.LP
	demand
	bidirectional
	pt\(hypt
	E
.sp 9p
.RT
.LP
		symmetric 
.LP
.sp 10
.bp
.sp 1P
.LP
	3)
	Access
.sp 9p
.RT
.ce
\fBH.T. [T6.241]\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) sw(48p) | cw(48p) sw(48p) | cw(36p) , c | c | c | c | ^ .
Signalling and OAM (Note 1)	User information	Support
Channel and rate	Protocols	Channel and rate	Protocols
_
.T&
cw(228p) .
Circuit mode
_
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(16)  	 {
I.430, I.440, I.441, I.450, I.451
(Note\ 2)
 }	B(64)  	I.430,  X.75 (SLP),  ISO 8208	A
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(64)  	 {
I.431, I.440, I.441, I.450, I.451
(Note\ 2)
 }	B(64)  	I.431,  X.75 (SLP),  ISO 8208	A
_
.T&
cw(228p) .
Packet mode
_
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(16)	 {
I.430, I.440, I.441, I.450, I.451, X.31
 }	B(64) or D(16)	 {
I.430,
X.25 LAPB,
X.25 (PLP)
 }	A
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(64)	 {
I.431, I.440, I.441, I.450, I.451, X.31
 }	B(64)	 {
I.431,
X.25 LAPB,
X.25 (PLP)
 }	FS
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
VC in B(64)	for further study	B(64)	FS	FS
.TE
.LP
\fINote\ 1\fR
\ \(em\ Definition of protocols for OAM is for further study.
.LP
\fINote\ 2\fR
\ \(em\ Demand services only. Others are for further study.
.nr PS 9
.RT
.ad r
\fBTable [T6.241], p. \fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.9
	\fIDynamic description\fR 
.sp 9p
.RT
.PP
The circuit mode dynamic description appears in
Recommendation\ I.220.
.RT
.sp 2P
.LP
\fB4\fR 	I.241.4\ \(em
	\fBMixed mode\fR 
.sp 1P
.RT
.PP
The prose definition of the mixed mode service is an extract of
Recommendation\ F.230.
.RT
.sp 1P
.LP
4.1
	\fIDefinition\fR 
.sp 9p
.RT
.PP
This service provides combined text and facsimile communication for end\(hyto\(hyend 
transfer of documents containing mixed information of text and fixed images. 
The high layer attributes are based on the CCITT Recommendations for 
Teletex and Telefax 4.
.RT
.sp 1P
.LP
4.2
	\fIDescription\fR 
.sp 9p
.RT
.PP
For further study.
.RT
.sp 1P
.LP
4.3
	\fIProcedures\fR 
.sp 9p
.RT
.PP
For further study.
.bp
.RT
.sp 1P
.LP
4.4
	\fINetwork capabilities for charging\fR 
.sp 9p
.RT
.PP
This Recommendation does not cover charging principles. Future
Recommendations in the D\(hySeries are expected to contain that information.
.PP
It shall be possible to charge the subscriber accurately for the
service.
.RT
.sp 1P
.LP
4.5
	\fIInterworking requirements\fR 
.sp 9p
.RT
.PP
For further study.
.RT
.sp 1P
.LP
4.6
	\fIInteraction with supplementary services\fR 
.sp 9p
.RT
.PP
For further study.
.RT
.sp 2P
.LP
4.7
	\fIAttributes and values of attributes of the mixed mode service\fR 
.sp 1P
.RT
.sp 1P
.LP
	a)
	\fILOW\ LAYER\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	\fIInformation transfer attributes\fR 
.LP
.sp 1
\fICircuit\(hymode bearer capability\fR \fIPacket\(hymode bearer capability\fR 
1. 
Information transfer
mode
circuit
packet
2.
Information transfer
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
.LP
3.
Information transfer capability
unrestricted (Note\ 1)
unrestricted
4.
Structure
unstructured (Note\ 2)
service data unit integrity
5.
Establishment of communication
demand
demand (VC), permanent (PVC)
.LP
6.
Symmetry
bidirectional symmetric
bidirectional symmetric
7.
Communication configuration
point\(hyto\(hypoint
point\(hyto\(hypoint
.rs
.sp 10P
.ad r
\fBblanc\fR 
.ad b
.RT
.LP
.bp
.LP
	\fIAccess attributes\fR 
.LP
.sp 1
\fICircuit\(hymode bearer capability\fR \fIPacket\(hy mode bearer capability\fR 
8. 
Access channel
B for user information
D for signalling
user information over virtual circuit within B\(hy or D\(hychannel. When
D\(hychannel is used, maximum packet size and quality of service may be
restricted. Signalling may be provided via D\(hychannel and/or virtual circuit
within B\(hychannel (Note\ 3)
.LP
9.
Access protocol
9.1
Signalling access protocol
layer 1
Rec. I.430/I.431
Rec. I.430/I.431
9.2
Signalling access protocol
layer 2
Rec. I.440/I.441
Rec. I.440/I.441, X.31
9.3
Signalling access protocol
layer 3
Rec. I.450/I.451
Rec. I.450/I.451, X.31
9.4
Information access protocol
layer 1
Rec. I.430/I.431
Rec. I.430/I.431
.LP
9.5
Information access protocol
layer 2
Rec. X.75 (SLP)
Rec. X.25 (LAPB)
9.6
Information access protocol
layer 3
ISO 8208
Rec. X.25 (PLP)
.sp 1P
.LP
	b)
	\fIHIGH\ LAYER\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	10.
	Type\ of\ user\ information:
	mixed mode
.LP
	11.
	Layer\ 4\ protocol\ functions:
	X.224, X.214
.LP
	12.
	Layer\ 5\ protocol\ functions:
	X.225, X.215
.LP
	13.
	Layer\ 6\ protocol\ functions:
	T.61, X.226, X.216
.LP
	13.1
	Resolution\ [pixels\ per\ inch\ (ppi)]:
	300\ \(mu\ 300
.LP
240\ \(mu\ 240
.LP
400\ \(mu\ 400 optional,
.LP
600, 1200
.LP
	14.
	Layer\ 7\ protocol\ functions:
	T.501, T.522, T.561
.sp 1P
.LP
	c)
	\fIGENERAL\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	15.
	Supplementary\ services\ provided:
	for further study
.LP
	16.
	Quality\ of\ service:
	for further study
.LP
	17.
	Interworking\ possibilities:
	ISDN Teletex, ISDN
Telefax\ 4
.LP
(others for further study)
.LP
	18.
	Operational\ and\ commercial:
	for further study
.PP
\fINote 1\fR \ \(em\ The interworking arrangements with networks having
restricted 64\ kbitB/Fs information transfer capability require further study.
.PP
\fINote 2\fR \ \(em\ Even if no structure is required the network may provide
8\ kHz integrity.
.PP
\fINote 3\fR \ \(em\ User information transferred via virtual channel on the
D\(hychannel is for further study.
.bp
.RT
.sp 1P
.LP
4.8
	\fIRecommended support of mixed mode by an ISDN\fR 
.sp 9p
.RT
.LP
	a)
	Overall support:
A
.LP
	b)
	Variation of non\(hydominant attributes:
.LP
	1)
	Information transfer mode
.LP
	\(em
	circuit:\ A
.LP
	\(em
	packet:\ A
.sp 2P
.LP
	2)
	\fIEstablishment\fR 	\fISymmetry\fR 	\fICommunication\fR 	\fISupport\fR 
	\fIof communication\fR 	\fIconfiguration\fR 	\fISupport\fR 
.sp 1P
.RT
.sp 1P
.LP
	demand
	bidirectional
	pt\(hypt
	E
.sp 9p
.RT
.LP
		symmetric 
.sp 1P
.LP
	3)
	Access
.sp 9p
.RT
.ce
\fBH.T. [T7.241]\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) sw(48p) | cw(48p) sw(48p) | cw(36p) , c | c | c | c | ^ .
Signalling and OAM (Note 1)	User information	Support
Channel and rate	Protocols	Channel and rate	Protocols
_
.T&
cw(228p) .
Circuit mode
_
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(16)  	 {
I.430, I.440, I.441, I.450, I.451
(Note\ 2)
 }	B(64)  	I.430,  X.75 (SLP),  ISO 8208	A
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(64)  	 {
I.431, I.440, I.441, I.450, I.451
(Note\ 2)
 }	B(64)  	I.431,  X.75 (SLP),  ISO 8208	A
_
.T&
cw(228p) .
Packet mode
_
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(16)	 {
I.430, I.440, I.441, I.450, I.451, X.31
 }	B(64) or D(16)	 {
I.430,
X.25 LAPB,
X.25 (PLP)
 }	FS
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(64)	 {
I.431, I.440, I.441, I.450, I.451, X.31
 }	B(64)	 {
I.431,
X.25 LAPB,
X.25 (PLP)
 }	FS
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
VC in B(64)	for further study	B(64)	for further study	FS
.TE
.LP
\fINote\ 1\fR
\ \(em\ Definition of protocols for OAM is for further study.
.LP
\fINote\ 2\fR
\ \(em\ Demand services only. Others are for further study.
.nr PS 9
.RT
.ad r
\fBTable [T7.241], p. \fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
4.9
	\fIDynamic description\fR 
.sp 9p
.RT
.PP
The circuit mode dynamic description appears in
Recommendation\ I.220.
.RT
.sp 2P
.LP
\fB5\fR 	I.241.5\ \(em
	\fBVideotex\fR 
.sp 1P
.RT
.PP
The prose description for the Videotex service in ISDN is for
further study and is intended to be based on Recommendation F.300.
.bp
.RT
.sp 1P
.LP
5.1
	\fIDefinition\fR 
.sp 9p
.RT
.PP
The Videotex service in the ISDN is an enhancement of the existing Videotex 
service with retrieval and mailbox functions for text (alpha) and 
graphic information.
.RT
.sp 1P
.LP
5.2
	\fIDescription\fR 
.sp 9p
.RT
.PP
For further study.
.RT
.sp 1P
.LP
5.3
	\fIProcedures\fR 
.sp 9p
.RT
.PP
For further study.
.RT
.sp 1P
.LP
5.4
	\fINetwork capabilities for charging\fR 
.sp 9p
.RT
.PP
This Recommendation does not cover charging principles. Future
Recommendations in the D\(hySeries are expected to contain that information.
.PP
It shall be possible to charge the subscriber accurately for the
service.
.RT
.sp 1P
.LP
5.5
	\fIInterworking requirements\fR 
.sp 9p
.RT
.PP
For further study.
.RT
.sp 1P
.LP
5.6
	\fIInteraction with supplementary services\fR 
.sp 9p
.RT
.PP
For further study.
.RT
.sp 2P
.LP
5.7
	\fIAttributes and values of attributes of the Videotex service\fR 
.sp 1P
.RT
.sp 1P
.LP
	a)
	\fILOW\ LAYER\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	\fIInformation transfer attributes\fR 
.LP
.sp 1
User to Videotex centre
Videotex centre to Videotex centre, external computers
1.
Information transfer mode:
circuit (Note\ 1)
circuit/packet
.LP
2.
Information transfer rate:
64 kbit/s
further study
3.
Information transfer capability:
unrestricted
further study
4.
Structure:
further study
further study
5.
Establishment of communication:
demand
demand/permanent
.LP
6.
Symmetry:
bidirectional symmetric
bidirectional symmetric
7.
Communication configuration:
point\(hyto\(hypoint
demand/permanent point\(hyto\(hypoint, multipoint
.bp
.LP
	\fIAccess attributes\fR 
.LP
	8.
	Access\ channel:
	B for user information (Note\ 2)
.LP
D for signalling
.LP
	9.
	Access\ protocol
.LP
	9.1
	Signalling\ access\ protocol\ layer\ 1:
	I.430/I.431
.LP
	9.2
	Signalling\ access\ protocol\ layer\ 2:
	I.440/I.441
.LP
	9.3
	Signalling\ access\ protocol\ layer\ 3:
	I.450/I.451
.LP
	9.4
	Information\ access\ protocol\ layer\ 1:
	I.430/I.431
.LP
	9.5
	Information\ access\ protocol\ layer\ 2:
	X.75 (SLP)
.LP
	9.6
	Information\ access\ protocol\ layer\ 3:
	ISO 8208
.sp 1P
.LP
	b)
	\fIHIGH\ LAYER\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	10.
	Type of user information:\ Videotex
	11.
	Layer 4 protocol functions
	
	
	12.
	Layer 5 protocol functions
	
	
	13.
	Layer 6 protocol functions
			\ For further study
	
	13.1
	Resolution [pixels per inch (ppi)]
	
	
	13.2
	Graphic mode
	
	
	14.
	Layer 7 protocol functions
	
.sp 1P
.LP
	c)
	\fIGENERAL\ ATTRIBUTES:\fR \ for further study
.sp 9p
.RT
.PP
\fINote 1\fR \ \(em\ The use of packet\(hymode is for further study.
.PP
\fINote 2\fR \ \(em\ The use of the D\(hychannel for Videotex information 
is for 
further study.
.RT
.sp 1P
.LP
5.8
	\fIRecommended support of Videotex by an ISDN\fR 
.sp 9p
.RT
.LP
	a)
	Overall support
: A
.LP
	b)
	Variations of non\(hydominant attributes:
.LP
	1)
	Information transfer mode
.LP
\(em
circuit
user terminal\(hyto\(hyVideotex centre
A
videotex centre to Videotex centre, external computer
A
\(em
packet
videotex centre to Videotex centre, external computer
A
.sp 2P
.LP
	2)
	\fIEstablishment\fR 	\fISymmetry\fR 	\fICommunication\fR 	\fISupport\fR 
	\fIof communication\fR 	\fIconfiguration\fR 	\fISupport\fR 
.sp 1P
.RT
.sp 1P
.LP
	demand
		bidirectional
	pt\(hypt
	E
.sp 9p
.RT
.LP
	
	permanent
		symmetric
.LP
	
	(Note)
	
.LP
	demand
		bidirectional
	multipoint
	A
.LP
	
	permanent
		symmetric
	(Note)
.LP
	
	(Note)
	
.PP
\fINote\fR \ \(em\ Between Videotex centres and to external
computers.
.bp
.sp 1P
.LP
	3)
	Access
.sp 9p
.RT
.ce
\fBH.T. [T8.241]\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) sw(48p) | cw(48p) sw(48p) | cw(36p) , c | c | c | c | ^ .
Signalling and OAM (Note 1)	User information	Support
Channel and rate	Protocols	Channel and rate	Protocols
_
.T&
cw(228p) .
Circuit mode
_
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(16)  	 {
I.430, I.440, I.441, I.450, I.451
(Note\ 2)
 }	B(64)  	I.430,  X.75 (SLP),  ISO 8208	A
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(64)  	 {
I.431, I.440, I.441, I.450, I.451
(Note\ 2)
 }	B(64)  	I.431,  X.75 (SLP),  ISO 8208	A
_
.T&
cw(228p) .
Packet mode
_
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(16)	FS	B(64) or D(16)	FS	FS
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(64)	FS	B(64)	FS	FS
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
VC in B(64)	FS	B(64)	FS	FS
.TE
.LP
\fINote\ 1\fR
\ \(em\ Definition of protocols for OAM is for further study.
.LP
\fINote\ 2\fR
\ \(em\ Demand services only. Others are for further study.
.nr PS 9
.RT
.ad r
\fBTable [T8.241], p. \fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
5.9
	\fIDynamic description\fR 
.sp 9p
.RT
.PP
The circuit mode dynamic description appears in
Recommendation\ I.220.
.RT
.sp 2P
.LP
\fB6\fR 	I.241.6\ \(em
	\fBTelex\fR 
.sp 1P
.RT
.sp 1P
.LP
6.1
	\fIDefinition\fR 
.sp 9p
.RT
.PP
This service provides interactive text communication. The digital signal 
at the SB/FT reference point follows the internationally agreed 
Recommendations for telex above the ISDN physical layer.
.RT
.sp 1P
.LP
6.2
	\fIDescription\fR 
.sp 9p
.RT
.PP
For further study.
.RT
.sp 1P
.LP
6.3
	\fIProcedures\fR 
.sp 9p
.RT
.PP
For further study.
.RT
.sp 1P
.LP
6.4
	\fINetwork capabilities for charging\fR 
.sp 9p
.RT
.PP
This Recommendation does not cover charging principles. Future
Recommendations in the D\(hySeries are expected to contain that information.
.PP
It shall be possible to charge the subscriber accurately for the
service.
.bp
.RT
.sp 1P
.LP
6.5
	\fIInterworking requirements\fR 
.sp 9p
.RT
.PP
For further study.
.RT
.sp 1P
.LP
6.6
	\fIInteraction with supplementary services\fR 
.sp 9p
.RT
.PP
For further study.
.RT
.sp 2P
.LP
6.7
	\fIAttributes and values of attributes of the telex service\fR 
.sp 1P
.RT
.sp 1P
.LP
	a)
	\fILOW\ LAYER\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	\fIInformation transfer attributes\fR 
.LP
	1.
	Information\ transfer\ mode:
	circuit (packet is for
further study (Note))
.LP
	2.
	Information\ transfer\ rate:
	64 kbit/s
.LP
	3.
	Information\ transfer\ capability:
	unrestricted
.LP
	4.
	Structure:
	8 kHz integrity
.LP
	5.
	Establishment\ of\ communication:
	reserved/permanent
.LP
	6.
	Symmetry:
	bidirectional
.LP
	7.
	Communication\ configuration:
	point\(hyto\(hypoint
.LP
	\fIAccess attributes\fR 
.LP
	8.
	Access\ channel:
	B for user information
.LP
D for signalling
.LP
(D for telex user information
is for further study (Note))
.LP
	9.
	Access protocol:
.LP
	9.1
	Signalling\ access\ protocol\ layer\ 1:
	I.430/I.431
.LP
	9.2
	Signalling\ access\ protocol\ layer\ 2:
	U.202
.LP
	9.3
	Signalling\ access\ protocol\ layer\ 3:
	U.202
.LP
	9.4
	Information\ access\ protocol\ layer\ 1:
	I.430/I.431
.LP
	9.5
	Information\ access\ protocol\ layer\ 2:
	U.202
.LP
	9.6
	Information\ access\ protocol\ layer\ 3:
	for further study
.sp 1P
.LP
	b)
	\fIHIGH\ LAYER\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	10.
	Type of user information:\ telex
	11.
	Layer 4 protocol functions
			12.
	Layer 5 protocol functions
			\ For further study
	
	13.
	Layer 6 protocol functions
	
	
	14.
	Layer 7 protocol functions
	
.sp 1P
.LP
	c)
	\fIGENERAL\ ATTRIBUTES\fR 
.sp 9p
.RT
.LP
	15.
	Supplementary\ services\ provided:
	for further study
.LP
	16.
	Quality\ of\ Service:
	for further study
.LP
	17.
	Interworking\ possibilities:
	Telex, Teletex (others: for further study)
.LP
	18.
	Operational\ and\ commercial:
	for further study
.LP
	\fINote\fR \ \(em\ Subject to satisfying telex quality of service on
D\(hychannel.
.sp 1P
.LP
6.8
	\fIRecommended support of Telex by an ISDN\fR 
.sp 9p
.RT
.LP
	a)
	Overall support:
FS
.LP
	b)
	Variations of non\(hydominant attributes:
.LP
	1)
	Information transfer mode
.LP
	\(em
	circuit: FS
.LP
	\(em
	packet: FS
.bp
.sp 2P
.LP
	2)
	\fIEstablishment\fR 	\fISymmetry\fR 	\fICommunication\fR 	\fISupport\fR  |
	\fIof communication\fR 	\fIconfiguration\fR 	\fISupport\fR  |
.sp 1P
.RT
.sp 1P
.LP
	demand
		pt\(hypt
	E
.sp 9p
.RT
.LP
		reserved
		bidirectional
	pt\(hypt
	FS
.LP
	
	permanent
		symmetric
	pt\(hypt
	A
		demand
		multipt
	A
.LP
		reserved
		bidirectional
	multipt
	FS
.LP
	
	permanent
		symmetric
	multipt
	A
.sp 1P
.LP
	3)
	Access
.sp 9p
.RT
.LP
.sp 1
.ce
\fBH.T. [T9.241]\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) sw(48p) | cw(48p) sw(48p) | cw(36p) , c | c | c | c | ^ .
Signalling and OAM (Note 1)	User information	Support
Channel and rate	Protocols	Channel and rate	Protocols
_
.T&
cw(228p) .
Circuit mode
_
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(16)  	 {
I.430, I.440, I.441, I.450, I.451
(Note\ 2)
 }	B(64)  	I.430, U.202 (Note\ 3)	FS
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(64)  	 {
I.431, I.440, I.441, I.450, I.451
(Note\ 2)
 }	B(64)  	I.431, U.202 (Note\ 3)	FS
_
.T&
cw(228p) .
Packet mode
_
.T&
cw(48p) | lw(48p) | cw(48p) | lw(48p) | cw(36p) .
D(16)	FS (Note\ 4)	D(16)	FS	FS
.TE
.LP
\fINote\ 1\fR
\ \(em\ Definition of protocols for OAM is for further study.
.LP
\fINote\ 2\fR
\ \(em\ Layer 2 and 3 protocols are for further study.
.LP
\fINote\ 3\fR
\ \(em\ Others are for further study.
.LP
\fINote\ 4\fR
\ \(em\ Subject to satisfying telex quality of service on D\(hychannel.
.nr PS 9
.RT
.ad r
\fBTable [T9.241], p. \fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
.sp 1
6.9
	\fIDynamic description\fR 
.sp 9p
.RT
.PP
For further study.
.RT
.LP
.sp 3
.bp