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GB/T 11589-1999 International user service categories and access types for public data networks and integrated services digital networks (ISDN)

Basic Information

Standard ID: GB/T 11589-1999

Standard Name: International user service categories and access types for public data networks and integrated services digital networks (ISDN)

Chinese Name: 公用数据网和综合业务数字网(ISDN)的国际用户业务类别和接入种类

Standard category:National Standard (GB)

state:in force

Date of Release1999-08-02

Date of Implementation:2000-03-01

standard classification number

Standard ICS number:Telecommunications, audio and video technology>>Telecommunications systems>>33.040.40 Data communications networks

Standard Classification Number:Communications, Broadcasting>>Communication Network>>M19 Technical Requirements for Interoperability of Communication Network Equipment and Communication Network Interfaces

associated standards

alternative situation:GB/T 11589-1989

Procurement status:eqv ITU-T X.1:1996

Publication information

publishing house:China Standards Press

other information

Release date:1989-08-21

Review date:2004-10-14

drafter:Xie Lin, Qiu Anding

Drafting unit:Data Communication Technology Research Institute of the Ministry of Posts and Telecommunications

Focal point unit:Telecommunications Science Research and Planning Institute of the Ministry of Posts and Telecommunications

Proposing unit:Ministry of Posts and Telecommunications of the People's Republic of China

Publishing department:State Administration of Quality and Technical Supervision

competent authority:Ministry of Information Industry (Telecommunications)

Introduction to standards:

This standard specifies the user service categories and access types of my country's public data network and integrated services digital network, and defines the data signal transmission rate, call control signal rate and the working method and access type of data terminal equipment. This standard applies to the user service categories and access types of public data network and integrated services digital network. GB/T 11589-1999 International user service categories and access types of public data network and integrated services digital network (ISDN) GB/T11589-1999 Standard download decompression password: www.bzxz.net

Some standard content:

National Standard of the People's Republic of China
GB/T11589—1999
eqvITU-TX.1:1996
International user classes of service in, and categoriesof access to,public data networks and integratedservices digital networks(ISDNs)Published on August 2, 1999
Implemented on March 1, 2000
State Administration of Quality and Technical Supervision
GB/T11589—1999
This standard is equivalent to the X.1 recommendation (1996 edition) formulated by the International Telecommunication Union (ITU-T). The writing format complies with the relevant provisions of GB/T1.1-1993 "Guidelines for Standardization Work Unit 1: Rules for Drafting and Presentation of Standards Part 1: Basic Provisions for the Writing of Standards".
This standard is the standard for user service categories and access types for my country's public data network and integrated services digital network. It defines four data transmission services: leased circuit, circuit switching, packet switching and frame relay. For each data transmission service, this standard specifies its DTE operation mode, data signal transmission rate, call control signal and code structure. ITU-T X.1 recommendation was significantly revised after 1984 (revised in Malaga-Torremolinos in 1984; revised in Melbourne in 1988; revised in Helsinki in 1993, and completed in 1996), merging and supplementing the relevant parts of X.1, X.2 and X.10 recommendations. Therefore, it is necessary to revise the corresponding standard GB/T11589-89 in my country. This revision of this standard adjusts and supplements some contents that are not in the original recommendation according to the latest requirements of the national standard formulation work, so the equivalent recommendation method is adopted.
The main revisions of this standard are as follows:
1 Added the foreword.
2 In the ITU-T preface, four new connection modes for public data transmission services and two access data transmission services are defined. 3 "Chapter 1 Scope" is added.
4 "Chapter 2 Referenced Standards" is added.
5 "Chapter 3 Abbreviations" is added.
6 Chapter 4 Access to Leased Circuit Data Transmission Services adds nine user service categories to the access of data terminal equipment operating in synchronous mode using the X.21 or X.21bis interface; adds access to data terminal equipment operating in start-stop mode using the X.21 or X.21bis interface.
7 Chapter 5 Access to Circuit Switched Data Transmission Services adds five user service categories to the access of data terminal equipment operating in start-stop mode using the X.21 or X.21bis interface; divides the access types into direct access and port access via ISDN in the access of data terminal equipment operating in synchronous mode using the X.21 or X.21bis interface, and adds four service categories. 8 Chapter 6 Access to packet switching data transmission services is divided into five parts according to the access mode (Table 5-9), and 32 user service categories are added to refine the access types. 9 A new "Chapter 7 Access to Frame Relay Data Transmission Services" is added. 10 Based on the opinions of experts, the English-Chinese comparison table of terms is retained and supplemented (Appendix A). This standard will replace GB/T11589-1989 from the date of implementation. This standard is proposed by the Ministry of Posts and Telecommunications of the People's Republic of China. This standard is under the jurisdiction of the Telecommunications Science Research and Planning Institute of the Ministry of Posts and Telecommunications. This standard is drafted by the Data Communication Technology Research Institute of the Ministry of Posts and Telecommunications. The main drafters of this standard are: Xie Lin and Qiu Anding. This standard was first issued in 1989.
This standard is entrusted to the Data Communication Technology Research Institute of the Ministry of Posts and Telecommunications for interpretation. I
GB/T11589—1999
ITU-T Foreword
Many countries have established public networks for data transmission and integrated services digital networks for integrated services, which require the development of standards for user service categories and access types. This standard requires the following: a) to provide a sufficient variety of data signal rates to meet the needs of users; b) to optimize the costs of data terminal equipment (DTE), transmission and switching in order to provide users with comprehensive and economical services; c) to recognize the special operating modes of some user data terminal equipment; d) to allow users to transmit information consisting of any bit sequence and any number of bits above a certain number; e) to recognize that the interaction between user requirements, technical limitations and tariff structure may affect the method by which DTE accesses public data transmission services.
User service category is a category of data transmission service, in which the DTE operating mode, data signal rate, call control signal rate and code structure (start and stop) should be standardized. Access category identifies the method used by DTE to access a specific data transmission service. There are four types of public data transmission services, namely: (1) Leased circuit data transmission service
(2) Circuit switching data transmission service
(3) Packet switching data transmission service
(4) Frame relay data transmission service
Data terminal equipment (DTE) can access data transmission services through any of the following connection methods: a) Direct access: when the DTE is connected to the network providing the service without passing through an intermediate switching network; b) Port access: when the DTE is connected to the network providing the service through an intermediate switching network (see Figure 1). Port access can be achieved through any of the following connections: (1) Switched connection: when signaling or control procedures are required to establish or release the connection between the DTE and the network providing the service; (2) Permanent connection: when signaling or control procedures are not required to establish or release the connection between the DTE and the network providing the service (see Figure 2). The types of access introduced in this standard take into account direct access (see note) to public data networks and ISDN as well as port access for interconnection with other public networks. It also includes the case of access to packet-switched data transmission services through PAD, FPAD or MAP functions as specified in the X.5 or X.8 recommendations of GB/T11591 standard. Note: Direct access can be provided by means of leased circuits or dedicated circuits. For example, packet terminals that meet user service categories 8 to 11 can access public packet-switched data transmission services through direct access (see the above note) or port access. Port access can be established using circuit-switched public data networks (CSPDNs), public switched telephone networks (PSTNs), ISDNs or PDNs that provide frame-relay data transmission services. In all these access cases, access to packet-switched data transmission services will require interworking functions, and permanent connection access and switched connection access can be used. It is not mandatory for the competent authorities to provide various data transmission services, user service categories or access types included in this standard. In addition, the access types for each user service category have not yet been recognized. Unrecognized access types are indicated by the symbol "-" in the following tables. 1
[Xinwang Hengmen made
or Xinerlu
) connect people
and push into the network
! 1 Scope National Standard of the People's Republic of China International user classes of service in, and categoriesof access to, public data networks and integratedservices digital networks (ISDNs) GB/T 11589—1999 ITU-TX.1:1996
Replaces GB/T11589-1989
This standard specifies the user service categories and access types of my country's public data network and integrated services digital network, and defines the data signal transmission rate, call control signal rate, and the working methods and access types of data terminal equipment. This standard applies to user service categories and access types of public data networks and integrated services digital networks. 2 Referenced standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T11590—1999 International data transmission services and optional user service facilities for public data networks (eqvITU-TX.2 Recommendation 1996)
GB/T11591—1989 Assembly and disassembly facilities in public data networks (idtITU-TX.3 Recommendation 1993) GB/T11592—1989 Interface between data terminal equipment (DTE) and data circuit terminating equipment (DCE) used to start/stop transmission services on public data networks (eqvITU-TX.20 Recommendation 1984) GB/T11593—1989 Data terminals working synchronously on public data networks Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) (eqyITU-TX.21 Recommendation 1984) GB/T11599—1989
GB/T11595—1989
GB/T11596—1989
Use of data terminal equipment (DTE) with synchronous V-series modem interface on public data networks (evITU-TX.21bis Recommendation 1984)
Packet data terminal equipment (DTE) and data circuit-terminating equipment (DCE) connected to public data networks using dedicated circuits Interface between (idtITU-TX.25 Recommendation 1996) Interface between DTE/DCE of assembly and disassembly facilities of start-stop data terminals entering the country's public data network (idtITU-TX.28 Recommendation 1997)
GB/T10198.3-1988 Technical requirements for fax machines Category III document fax machines (idtITU-TT.4 Recommendation 1980)GB/T2886-1992 Technical conditions for intercommunication of Category II document fax machines in the telephone network (idtITU-1T.30 Recommendation 1982)YD/T891-1997 Relay data transmission service provided through dedicated circuits Public data networks for data transmission using the interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) (idtITU-TX.36 Recommendation 1996) ITU-TX.4 Recommendation (1988) General structure of international code 5 signals for data transmission on public data networks ITU-TX.5 Recommendation (1996)
ITU-TX.8 Recommendation (1994)
ITU-TX.30 Recommendation (1993)
Fax Packaging and Disassembly Device (FPAD) in Public Data Networks Multi-Function Packaging and Disassembly Device (MAP) Framework and service interface definition Comprehensive business ISDN is a data terminal that complies with X21, X.21bis, and X.20bis. Approved by the State Administration of Quality and Technical Supervision on August 2, 1999 and implemented on March 1, 2000. ITU-TX.31 Recommendation (1995) ITU-TX.32 Recommendation (1996) ITU-TX.34 Recommendation (1996) ITU-TX.38 Recommendation (1996) ITU-TX.52 Recommendation (1988) ITU-TX.213 Recommendation (1995) ||ITU-TX.223 Recommendation (1993)
ITU-TX.301 Recommendation (1993)
3 Abbreviations
B-ISDN
GB/T11589—1999
Support for packet-based terminal equipment (DTEs)
Integrated Services Digital Network (ISDN) Support for packet-based terminal equipment Interface between packet-based data terminal equipment (DTE) and data circuit-terminating equipment (DCE) that access a packet-switched public data network via a public switched telephone network, an integrated services digital network, or a circuit-switched public data network
B-ISDN DN access packet switching data transmission service Category 3 fax machine access to the national data network fax packet assembly and disassembly equipment (FPAD) Category 3 fax machine/DCE interface used
Method of encoding non-isochronous signals into synchronous user bearer channels Definition of network services for open systems interconnection for ITU applications using X.25 to provide OSI connection network services for ITU applications Description of general configuration for call control within and between subnets for providing data transmission services
Broadband integrated services digital network
Circuit switching data network
Circuit switching public data network
Data circuit terminating equipment|| tt||Data terminal equipment
Fax assembly and disassembly equipment
Ton-relay bearer service
Ton-relay data transmission service
Ton-relay public data network
International Electrotechnical Commission
International Organization for Standardization
Integrated Services Digital Network
International Telecommunication Union
Multi-function assembly and disassembly equipment
Assembly and disassembly equipment
Public data network
Packet switching public data network
Public switched telephone network
4 Access leased circuit data transmission service
See Table 1 and Table 2.
Access user service category of data terminal equipment operating in synchronous mode using X.21 or X.21bis interface
Data signal transmission rate during data transmission phase (Note)
600 bit/s
2400 bit/s
4800 bit/s
Access type
Direct access
User service category
GB/T11589—1999
Table 1 (End)
Data signal transmission rate during data transmission phase (Note)
9600 bit/s
48kbit/s
64kbit/s
128kbit/s
192kbit/s
256kbit/s
384kbit/s
512kbit/s
1024kbit/s
1536kbit/s
1920kbit/s
Access categories
Direct access
Note: In ISDN, these user service categories are supported using terminal adapters (compliant with Recommendation X.30). The concept of terminal adapter functional combination is defined in Recommendation 1.411.
2 Access table 2 for data terminal equipment operating in start-stop mode using X.20 or X.20bis interface
User service category
Data signal transmission rate and code structure in data transmission phase (Note)
300 bit/s, 11) unit/character, start-stop mode 50~200 bit/s, 7.5~11* unit/character, start-stop mode 600 bit/s, 10 unit/character, start-stop mode 1200 bit/s, 10 unit character character, start and end type 2400bit/s, 10 unit character, start and end type 4800bit/s, 10 unit/character, start and end type 9600bit/s, 10 unit/character, start and end type Access type
Direct access
Note: For terminals operating at data signal transmission rates of 600bit/s, 1200bit/s, 2400bit/s, 4800bit/s, and 9600bit/s, some competent authorities provide leased circuit asynchronous services. These services are supported by bearer channels of synchronous networks with asynchronous-synchronous coding. For data signal transmission rates of 600bit/s, 2400bit/s, 4800bit/s and 9600bit/s, the asynchronous-synchronous coding specified in the V.14 recommendation is used. For the rate of 1200bit/s, the asynchronous-synchronous coding specified in the X.52 recommendation is used. a) Use the provisions of the X.4 recommendation.
5 Access to circuit switched data transmission services
See Tables 3 and 4.
3 Use X.20 or X.Access of data terminal equipment with 20bis interface in start-stop mode (Note 1) Table 3
Data signals in data transfer phase
User service category
Transmission rate and code structure
(Note 2)
300bit/s, 11° unit/character, start-stop mode 50200bit/s, 7.5~11*) unit/character, start-stop mode (Note 3 and Note 4)
600bit/s, 10 units/character, start-stop mode Call control in call control phase Signal
300bit/s, international 5 number (11 units/characters), start-stop
200bit/s, international 5 number (11 units/characters), start-stop (see Note 5)
600bit/s, international 5 number (10 units/characters), start-stop
Access type
Direct access
User service category
GB/T11589—1999
End of Table 3)
Data transmission phase Data signal
Transmission rate and code structure
(Note 2)
1200bit/s, 10 units/character, start-stop2400bit/s, 10 units/character, start-stop4800bit/s, 10 units/character, start-stop9600bit/s, 10 units/character, start-stopCall control signal in call control stage
1200bit/s, international 5 number (10 units/character), start-stop
2400bit/ s, international 5 number (10 units/character), start-stop
4800bit/s, international 5 number (10 units/character), start-stop
9600bit/s, international 5 number (10 units/character), start-stop
Access category
Direct access
1There is no user service category with a data rate of 50bit/s, 7.5 unit start-stop character transmission mode and address selection and call proceeding signaling with an international 2 number at a rate of 50bit/s. However, a few administrations have indicated that they will provide user telegraph services (50 baud, international 2 numbers) as one of the multiple services of their public data networks. 2For user service categories 1, 2 and 15, the bearer channel of the synchronous network is used, and asynchronous-synchronous coding is performed in accordance with the provisions of the X.52 recommendation. For user service categories 14, 16, 17 and 18, the asynchronous-synchronous coding specified in the V.14 recommendation is used. 3 During the data transfer phase, user service category 2 shall provide operation at the following data signalling rates and code structures: 50 bit/s, (7.5 units/character)
100 bit/s, (7.5 units/character)
110 bit/s, (11 units/character)
134.5 bit/s, (9 units/character)
200 bit/s, (11 units/character)
Call control signals shall be 200 bit/s, international 5 numbers (11 units/character). 4 For international user service category 2, it should be noted that some public data networks may not prevent two terminals with different data signalling rates and different code structures from being connected together by circuit switching. 5 Some administrations have indicated that, for some of the data signalling rates listed in Note 3 above, they allow service category 2 users to operate at the same signalling rates and code structures for both data transfer and address selection, and also to use these rates and code structures for receiving call proceeding signals. Call control signals use international 5 numbers and the corresponding parts of GB/T11592 standard should be used. a) Use the provisions of X.4 recommendation.
Table 4 Data in the access data transmission phase of data terminal equipment operating in synchronous mode using X.21 or X.21bis interface
User service category
Signal transmission rate
(Note 1)
600bit/s
2400bit/s
4800bit/s
9600bit/s
48kbit/s
64kbit/s
Call control signals in the call control phase
(Note 2, Note 3)
600bit /s, International 5 number
2400bit/s, International 5 number
4800bit/s, International 5 number
9600bit/s, International 5 number
48kbit/s, International 5 number
64kbit/s, International 5 number
Access type
Port access via ISDN
Direct access
(Note 4, Note 5)
Permanent connection
Switched connection
User service category
Data in data transmission phase
Signal Transmission rate
(Note 1)
384kbit/s
1536kbit/s
1920kbit/s
GB/T11589-1999
Table 4 (end)
Call control signals in the call control phase
(Note 2, Note 3)
384kbit/s, international 5 number
1536kbit/s, international 5 number
1920kbit/s, international 5 number
Access type
Port access via ISDN Input
Direct access
(Note 4, Note 5)
Permanent connection Switched connection
1 For terminals that use 600bit/s, 1200bit/s, 2400bit/s, 4800bit/s, 9600bit/s, 10-unit start-stop characters in the data transmission phase, and use: 600bit/s, 1200bit/s, 2400bit/s, 4800bit/s, 9600bit/s, international 5 numbers and 10-unit start-stop characters in the call control phase, some administrations provide circuit-switched asynchronous services. These services are supported by synchronous network bearer channels. For user service categories 1 and 2 and rates of 1200 bit/s, the asynchronous-synchronous coding specified in the X.52 recommendation is used. For data signal transmission rates of 600 bit/s, 2400 bit/s, 4800 bit/s and 9600 bit/s, the asynchronous-synchronous coding specified in the V.14 recommendation is used. 2 Applicable only to interfaces of the GB/T11593 standard. 3 For user service categories 30 and above, the characteristics at reference point R are to be determined. 4 In ISDN, these user service categories can be supported using terminal adapters (compliant with the X.30 recommendation). The concept of terminal adapter functional combination is defined in the 1.411 recommendation.
5 The control signals used by access categories S6 to S9 and R6 to R9 are the same as those call control signals defined on the ISDN reference point S/T. For interfaces at reference point R, refer to the user service categories corresponding to the same data signal transmission rate in this table. Reference points R, S and T are defined in the I.411 recommendation.
6 Access packet switching data transmission service
See Tables 5 to 9.
Data signal
Transmission rate
2400bit/s
4800bit/s
9600bit/s
14400bit/s
48kbit/s
1200bit/s
64kbit/s
128kbit/s
Use X.25, X.32, X.34 or X.36 Interface Data terminal equipment operating in synchronous mode Access to services provided by PSPDN
Direct access and permanently connected port access (Note 1) Access type
Services provided by PSPDN
Port access
(Note 3)
Via ISDN
Permanent connection
(B/H channel)
(Note 2 to Note 5)
(Note 6)
Via ISDN
(FRDTS)
B/H channel
Via ISDN
(FRDTS)
D channel
B-ISDN
(Note 7)|| tt||Data signal
Transmission rate
192kbit/s
256kbit/s
320kbit/s
384kbit/s
448kbit/s
512kbit/s
576kbit/s
640kbit/s
704kbit/s
768kbit/s
832kbit/s
896kbit/s
960kbit/s
1024kbit/s
1088kbit/s s
1152kbit/s
1216kbit/s
1280kbit/s
1344kbit/s
1408kbit/s
1472kbit/s
1536kbit/s
160 0kbit/s
1664kbit/s
1728kbit/s
1792kbit/s
1856kbit/s
1920kbit/s
1984kbit/s
2048kbit/s||t t||(Note 3)
GB/T11589—1999
Table 5 (end)
Access types
Services provided by PSPDN
Port connection
Permanent connection
Via ISDN
(B/H channel)
(Note 2 to Note 5)
(Note 6)
Via ISDN
(FRDTS)
B/H channel
Via ISDN
(FRDTS)
D channel
Packet switched data transmission service allows communication between data terminal equipment operating at different data signaling rates. These user service categories in ISDN can be supported via
B-ISDN
(Note 7)
using terminal adapters (compliant with Recommendation X.31). The concept of terminal adapter functional combination is defined in Recommendation I.411.
3 Recommendation X.31 (Case A) applies in the following cases: - at the S/T reference point, when access categories D5 and Q5 are provided over an ISDN B channel; - at the S/T reference point, when access categories D9, D12, D13, Q6, Q7 and Q8 are provided over an ISDN H channel; at the R reference point, when access categories D1, D2, D3, D4, D5, Q1, Q2, Q3.Q4 and Q5 are provided over an ISDN B channel with a terminal adapter.
4 Recommendation X.31 (Case A) and Recommendation X.32 apply at the S/T reference point. Recommendation X.32 applies at the R reference point. 5 For user service categories 30 and above, the characteristics at the R reference point are to be determined. 6 Use X.36 recommendations.
Use X.34 recommendations.
GB/T11589—1999
5 Data terminals operating in synchronous mode using X.25, X.32, X.34 or X.36 interfaces Table 6
Equipment access to services provided by PSPDN
Port access to switched connections (Note 1)
Access type
Services provided by PSPDN
Port access
Data signal
Transmission rate
2400bit/s
4800bit/s
9600bit/s
14400bit/s
48kbit/s
1200bit/s
64kbit/s
128kbit/s
192kbit/ s
256kbit/s
320kbit/s
384kbit/s
448kbit/s
512kbi t/s
576kbit/s
640kbit/s
704kbit/s
768kbit/s
832k bit/s
896kbit/s
960kbit/s
1024kbit/sbzxZ.net
1088kbit/s
1152kbit/s
1216kbit/s
1280kbit/s
1344kbit/s
1408kbit/ s
1472kbit/s
1536kbit/s
1600kbit/s
1664kbit/s
17 28kbit/s
1792kbit/s
1856kbit/s
1920kbit/s
1984kbit/s| |tt||(Note 4)
Via ISDN
(B/H channel)
(Note 2 Note 5)
Switch connection
(Note 6)
Via ISDN
(FRDTS)
B/H channel
Via ISDN
(FRDTS)
D channel
B-ISDN|| tt||(Note 7)
Data signal
Transmission rate
2048kbit/s
GB/T11589—1999
Table 6 (End)
Access types
Services provided by PSPDN
Port access
Switched connection
(Note 4)
Via ISDN
(B/H channel)
(Note 2 to Note 5)
(Note 6)
Via ISDN
(FRDTS)
B/H channel
Via ISDN
(FRDTS)
D channel
1 Packet switched data transmission service allows communication between data terminal equipment operating at different data signal transmission rates. These user service categories in ISDN can be supported via
B-ISDN
(Note 7)
2 The use of terminal adapters (compliant with Recommendation X.31) is supported. The concept of terminal adapter functional combination is defined in Recommendation I.411.
3 Recommendation X.31 (Case A) applies in the following cases: - at the S/T reference point, when access categories D5 and Q5 are provided over an ISDN B channel, - at the S/T reference point, when access categories D9, D12, D13.Q6, Q7 and Q8 are provided over an ISDN H channel, - at the R reference point, when access categories D1, D2, D3, D4, D5, Q1, Q2, Q3, Q4 and Q5 are provided over an ISDN B channel with a terminal adapter.
4 Recommendation X.31 (Case A) and Recommendation X.32 apply at the S/T reference point. Recommendation X.32 applies at the R reference point. 5 For user service categories 30 and above, the characteristics at the R reference point are to be determined 6 Use X.36 recommendations.
7 Use X.34 recommendations.
Data signaling
Transmission rate
Use X.25, X.32, X.34 or X.36 Interface Data terminal equipment operating in synchronous mode accesses services provided by ISDN (Note 1) Access type
Services provided by ISDN
Direct access
B/H channel
(Note 2, Note 4)
2400bit/s
4800bit/s
9600bit/s
14400bit/s
48kbit/s
1200bit/s
64kbit/s
128kbit/s
192kbit/s
256kbit/s
320kbit/s
38 4kbit/s
448kbit/s
D channel
(Note 6)
Permanent connection
Via ISDN
(FRDTS)
B/H channel
Via ISDN
(FRDTS)
D channel
Port switch connection
B-ISDN
(Note 7)
(Note 6)
Via ISDN
(FRDTS)
B/H channel
Via ISDN
(FRDTS)
D channel
B-ISDN
(Note 7)
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