1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 ) TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU).4%2!4%$G0G03%26)#%3G0G0$)4!,G0G0.%47/2+G0 )3$.G93%26)#%G0G0#!0!“),)4)%34%,%3%26)#%3G0G03500/24%$G0G0“9G0G0!.G0G0)3$. 4%,% the calling subscriber will have full control of the Group 4 facsimile call.3.3. Pro
2、cedures3.3.1 Provision/withdrawalThe national and international Telefax 4 service shall be open continuously.Telefax 4 terminals for which call numbers are published in the directories shall, in principle, be available toaccept calls continuously.2 Fascicle III.7 - Rec. I.241.3In order to facilitate
3、 the 24-hour duration of service it is permitted to use a centralized storage in the network torealize the receiving memory capability of the terminal.3.3.2 Call phasesThe operations for each call may be divided into the following three phases:a) preparation: preparation of the information to be tra
4、nsmitted;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 tocontrol procedures.c) outpu
5、t: displaying the message either by immediate printing or from a storage medium upon control by theoperator.Note - The information may consist of one or more Telefax 4 documents each consisting of one or moreTelefax pages.The control procedures as specified in Recommendation T.62 and Recommendations
6、 of the T.400-Series shallbe used as end-to-end communication procedures between terminals in the service.The low layer protocols and the network independent basic transport protocol for Telefax 4 are specified inRecommendations T.70 and T.90.The network-dependent control procedures for the Telefax
7、4 service are those that are defined for ISDN.3.3.3 Call identification lineThe Telefax 4 procedures include the exchange of reference information prior to sending any document. Thisreference information includes identification of the parties to the call as well as the date and time. Also, supplemen
8、taryreference information is exchanged during a call to allow reference to an individual document or page for error recoveryor other purposes. Date and time have to be provided by the network and sent to the calling terminal in the call set-upphase.This reference information, taken together, is defi
9、ned to be printable on a single line called the callidentification line. Use of this information is a local decision except in recovering from an interrupted transmission. Inthe case of automatic linking, the use of this information is for further study.For the format of the call identification line
10、 see Recommendation F.200.3.3.4 Error protectionTo ensure call integrity, error protection will be provided by Telefax 4 control procedures (seeRecommendations T.62, T.70 and T.90). Besides the error detection and correction mechanism in layer 2 (and 3) anadditional error detection and correction me
11、chanism is provided in the session layer. By this mechanism, errors of thehigher layer functions (e.g. command/response sequence error) and transmission errors, which are not corrected by thelower layers, will be corrected, for example, by retransmission of one or several pages.The error rate on the
12、 pre-information, information and post-information phases should not exceed 1 10-6.3.4 Network capabilities for chargingThis Recommendation does not cover charging principles. Future Recommendations in the D-Series areexpected to contain that information.It shall be possible to charge the subscriber
13、 accurately for the service.Fascicle III.7 - Rec. I.241.3 33.5 Interworking requirements3.5.1 Within the Telefax 4 service, interworking between terminals connected to different networks is required for:a) Telefax 4 (ISDN) - Telefax 4 (CSPDN: Circuit switched public data network)b) Telefax 4 (ISDN)
14、- Telefax 4 (PSPDN: Packet switched public data network)c) Telefax 4 (ISDN) - Telefax 4 (PSTN: Public switched telephone network)In the case of international interworking between Group 4 facsimile terminals connected to dissimilarnetworks, Recommendation X.300 shall apply. For international interwor
15、king between PSTN and ISDN, a (separate)Telefax 4 interworking unit may be necessary.International routes between ISDNs for the Telefax 4 service shall be capable of supporting user data rates upto 64 kbit/s.3.5.2 Intercommunication with other services3.5.2.1 Intercommunication between basic mode an
16、d mixed mode Teletex terminals and Classes I, II and III Group 4facsimile terminals connected to the Telefax 4 service is shown in Table 1/I.241.3.In both the Teletex and Telefax 4 services, the equipment providing mixed mode should enable a directexchange of documents in accordance with Recommendat
17、ions T.6, T.61 and of the T.400-Series.TABLE 1/I.241.3Current status of direct intercommunicationfor Teletex and Group 4 facsimile terminals on the same networkT: Basic Teletex document with character coded information only.F: Group 4 facsimile document with facsimile coded information only.MM: Mixe
18、d-mode document with character and facsimile coded information.PM1: Processable mode document with character coded information only.ToFromFacsimileGroup 4,Class IFacsimileGroup 4,Class IIFacsimileGroup 4,Class IIITeletexbasic modeTeletexmixed modeTeletexprocessablemode 1Facsimile Group 4,Class IFFFF
19、acsimile Group 4,Class IIFFFFacsimile Group 4,Class IIIF T, F, MM T, F, MM T T, MM TTeletex basic mode T T T T TTeletex mixed mode T, MM T, MM T T, MM TTeletex processablemode 1T T T T T, PM14 Fascicle III.7 - Rec. I.241.33.5.2.2 Intercommunication is desirable between terminals of the Telefax 4 ser
20、vice and terminals of services otherthan Telefax 4 provided over ISDN and other public switched networks.Intercommunication possibilities between Telefax 4 terminals and Telefax 3 terminals have to be provided (seealso Recommendation F.180):a) Telefax 4 (ISDN) - Telefax 3 (PSTN)b) Telefax 4 (ISDN) -
21、 Telefax 3 (ISDN, via terminal adaptors)In case a) Telefax 4 terminals use specific service features in ISDN. Intercommunication should be supportedby ISDN-PSTN interworking units.In case b) Telefax 3 terminals and Telefax 4 terminals which are to be connected in the PSTN can also beconnected to the
22、 ISDN via terminal adaptors.3.6 Interaction with supplementary servicesEach supplementary service description identifies the applicability with this teleservice.For the ISDN, the international supplementary services for the Telefax 4 service in the circuit mode using a B-channel are:i) closed user g
23、roup;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 supplementa
24、ry services is for further study.Supplementary services for Telefax 4 with a packet mode of operation are for further study.3.7 Attributes and values of attributes of the Telefax 4 servicea) LOW LAYER ATTRIBUTESInformation transfer attributesCircuit-mode bearer capability Packet-mode bearer capabili
25、ty1. Information transfer mode circuit packet2. Information transfer rate 64 kbit/s maximum throughput of a givenvirtual circuit is less than or equalto the maximum bit rate of theuser information access channeland the throughput class of thevirtual circuit3. Information transfer capability unrestri
26、cted (Note 1) unrestricted4. Structure unstructured (Note 2) service data unit integrity5. Establishment ofcommunicationdemand demand (VC)/ permanent (PVC)6. Symmetry bidirectional symmetric bidirectional symmetric7. Communication configuration point-to-point point-to-pointFascicle III.7 - Rec. I.24
27、1.3 5Access attributesCircuit-mode bearer capability Packet-mode bearer capability8. Access channel: B for user informationD for signallingUser information over virtualcircuit within B- or D-channel.When D-channel is used,maximum packet size and qualityof service may be restricted.Signalling may be
28、provided via D-channel and/or virtual circuitwithin B-channel.9. Access protocol9.1 Signalling access protocollayer 1:Rec. I.430/I.431 Rec. I.430/I.4319.2 Signalling access protocollayer 2:Rec. I.440/I.441 Rec. I.440/I.441, X.319.3 Signalling access protocollayer 3:Rec. I.450/I.451 Rec. I.450/I.451,
29、 X.319.4 Information access protocollayer 1:Rec. I.430/I.431 Rec. I.430/I.4319.5 Information access protocollayer 2:Rec. X.75 (SLP) Rec. X.25 (LAPB)9.6 Information access protocollayer 3:ISO 8208 Rec. X.25 (PLP)b) HIGH LAYER ATTRIBUTES10. Type of user information : Telefax 411. Layer 4 protocol func
30、tions: T.7012. Layer 5 protocol functions: T.6213. Layer 6 protocol functions: T.400-Series (Note 4)13.1 Resolution pixels per inch (ppi): 200 200 standard;240 240, 300 300, 400 400 optional14. Layer 7 protocol functions: T.503, T.521, T.563c) GENERAL ATTRIBUTES15. Supplementary services provided: s
31、ee 3.616. Quality of service: for further study17. Interworking possibilities: see 3.518. Operational and commercial: for further studyNote 1 - The interworking arrangements with networks having a restricted 64 kbit/s information transfercapability require further study.Note 2 - Even if no structure
32、 is required the network may provide 8 kHz integrity.Note 3 - User information transferred via virtual channel on the D-channel is for further study.Note 4 - Further study is required to identify a more precise reference in the T.400-Series ofRecommendations.6 Fascicle III.7 - Rec. I.241.33.8 Recomm
33、ended support of Telefax 4 by an ISDNa) Overall support1: Ab) Variations of non-dominant attributes:1) Information transfer modeNote - In the interim period, the circuit mode method of operation is preferred. circuit: A packet: A2) Establishment Symmetry Communication Support1of communication config
34、uration_demand bidirectional pt-pt Esymmetric3) AccessNote 1 - Definition of protocols for OAM is for further study.Note 2 - Demand services only. Others are for further study.3.9 Dynamic descriptionThe circuit mode dynamic description appears in Recommendation I.220.1The definition of E (essential)
35、 and A (additional) can be found in Recommendation I.240.Signalling and OAM(Note 1)User informationSupportChannel and rate Protocols Channel and rate ProtocolsCircuit modeD(16) I.430, I.440, I.441,I.450, I.451(Note 2)B(64) I.430,X.75 (SLP),ISO 8208AD(64) I.431, I.440, I.441,I.450, I.451(Note 2)B(64) I.431,X.75 (SLP),ISO 8208APacket modeD(16) I.430, I.440, I.441,I.450, I.451, X.31B(64) or D (16) I.430,X.25 LAPB,X.25 (PLP)AD(64) I.431, I.440, I.441,I.450, I.451, X.31B(64) I.431,X.25 LAPB,X.25 (PLP)FSVC in B(64) for further study B(64) FS FS
