GB/T 11593-2001 Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) operating synchronously on public data networks

This standard defines the physical characteristics and call control procedures of the common interface between DTE and DCE, and is applicable to the user service categories using synchronous transmission defined in GB/T 11589. GB/T 11593-2001 Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) working synchronously on public data networks GB/T11593-2001 Standard download decompression password: www.bzxz.net

ICS33.040.40
National Standard of the People's Republic of China
GB/T11593-2001
eqyITU-TX.21:1992
Interface between data terminal equipmentand data circuit-terminating equipment forsynchronous operation on public data networks networks2001-11-05 Issued
People's Republic of China
General Administration of Quality Supervision, Inspection and Quarantine
2002-06-01 Implementation
GB/T11593—2001
ITU-T Foreword
Referenced Standards
Abbreviations
Elements of the DTE/DCE physical interface
Synchronization and error checking of call control characters Elements of the call control phase in circuit switching services Data transfer phase·
Clearing phase
Test loop
Interface signalling state diagram
Appendix A (Standard Appendix)
Appendix B (Standard Appendix)
Appendix C (Standard Appendix)
Appendix D (Standard Appendix)
Appendix E (Standard Appendix)
Appendix F (Standard Appendix) Appendix G (Appendix to the standard)
Appendix H (Appendix to the standard)
Appendix 1 (Appendix to the standard)
Appendix J (Suggestive Appendix)
Interface signaling sequence diagram and timeout operation
DTE time limit and DCE timeout
Format of selection signal, call progress signal and information signal provided by DCEIntercommunication between DTE conforming to this standard and DTE conforming to GB/T11599 standardCoding of call progress signal and information provided by DTE…Coding of service facility requests, indicators and parametersInformation content of information provided by DCE
Cross-reference and status transition table
English-Chinese comparison table of terms
GB/T11593-2001
This standard equivalently adopts the X.21 recommendation (1992 edition) formulated by the International Telecommunication Union (ITU-T). In order to adapt to the development of data communication, ITU-T X.21 recommendation was revised twice after 1984 (revised in Malaga-Torremolinos in 1988; revised again in 1992), so it is necessary to revise the corresponding standard GB/T11593-1989 in my country. This standard is the standard for the intercommunication between synchronous data terminal equipment and data circuit terminating equipment on my country's public data network. It defines the physical interface between equipment and the signaling process on the user line during intercommunication. The format of this standard complies with the relevant provisions of GB/T1.11993 Standardization Work Guide Unit 1: Drafting and Expression Rules of Standards Part 1: Basic Provisions for Standard Writing. And as required, Chapter 1 Scope, Chapter 2 Reference Standards and Chapter 3 Abbreviations are added, so the equivalent recommendation method is adopted. Appendix A, Appendix B, Appendix C, Appendix D, Appendix E, Appendix F, Appendix G, Appendix H, and Appendix I of this standard are all appendices to the standard; Appendix "" is a prompt appendix.
The main revisions to this standard are as follows:
1 Added Chapter 1 Scope, Chapter 2 Reference Standards and Chapter 3 Abbreviations. 2 Added some definitions, operations and notes in Chapter 4. 3 Added some definitions and operations in Chapter 6, Chapter 8 and Chapter 9. 4 Added some operations and notes in Appendix A, Appendix B, Appendix C and Appendix D. 5 Added some instructions and definitions in Appendix F, Appendix G and Appendix H. 6 Deleted, modified and added some status numbers in Appendix 1. 7 Retained the English-Chinese comparison table of nouns (Appendix J). From the date of implementation, this standard will replace GB/T11593-1989. This standard was proposed by the Ministry of Information Industry of the People's Republic of China. This standard is under the jurisdiction of the Telecommunication Research Institute of the Ministry of Information Industry. This standard was drafted by the Data Communication Science and Technology Research Institute of the Ministry of Information Industry. The main drafters of this standard are: Xie Lin and Qiu Anding. This standard is entrusted to the Data Communication Science and Technology Research Institute of the Ministry of Information Industry for interpretation. This standard was first published in 1989.
GB/T11593-2001
ITU-T takes into account:
ITU-T Foreword
a) Recommendations X.1 and X.2 define the services and service facilities provided by public data networks; b) Recommendation X.92 defines the hypothetical reference connection used by synchronous public data networks: c) Recommendation X.96 defines call progress\signaling, d) the necessary requirements of an interface recommendation should be defined according to the hierarchy of the architecture; e) people hope to standardize the interface characteristics between data terminal equipment (DTE) and data circuit terminating equipment (DCE) in public data networks.
Therefore, it is unanimously recommended that:
For user service categories using synchronous transmission on public data networks, the interface between DTE and DCE should comply with the definition of this recommendation. 1 Scope
National Standard of the People's Republic of China
Interface between data terminal cquipmentand data circuit-terminating equipment forsynchronous operation on public data networksGB/T11593—2001
eqvITU-T X.21:1992
Replaces GB/T11593-1989
1.1 This standard defines the physical characteristics and call control procedures of the common interface between DTE and DCE, and is applicable to user service categories using synchronous transmission defined in GB/T11589. 1.2 This standard includes the formats and procedures of "select", "call proceeding" and "information provided by DCE" signals. 1.3 Contains provisions for duplex operation.
1.4 The operation of the half-duplex interface connecting the DTE and the data circuit in accordance with GB/T11599 is described in Appendix E. The half-duplex operation between DTEs in accordance with this standard is subject to further study when this new service facility is recognized. 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/T11589-1999 International user service categories and access types for public data networks and integrated services digital networks (ISDN) (eqv ITU-T X.1.1996)
GB/T11590—1999
International data transmission services and optional user facilities for public data networks and ISDN networks (eqvITU-TX.2 Recommendation 1996)
GB/T11599—1989 Use of data terminal equipment (DTE) with synchronous V-series modem interface on public data networks (eqvCCITTX.21bis:1984)
GB/T7618—1987
Electrical characteristics of unbalanced two-stream interface circuits commonly used with integrated circuit devices in the field of data communications (eqvCCITTV.10:1984)
GB/T7619— 1987 Electrical characteristics of balanced two-stream interface circuits commonly used with integrated circuit devices in the field of data communications (cqvCCITTV.11:1984)
ITU-TX.4:1988 2
General structure of international 5-number signals for data transmission on public data networks ITU-TX.24:1988 Definition table of interface circuits between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) used in public data networks
ITU-TX.96:1993
Call proceeding signals for public data networks
ITU-TX.121:1996 5
International numbering plan for public data networks
ITU-TX.150:1988 Principles for Maintenance Testing of Public Data Networks Using Data Terminal Equipment (DTE) and Data Circuit-terminating Equipment Test Loops
Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on November 5, 2001 and implemented on June 1, 2002
3 Abbreviations
AAS Abbreviated Address Signal
AS Address Signal
CPS Call Proceeding Signal
DCC Data Country Code
Data Circuit-terminating Equipment
DNIC Data Network Identification Code
Data Switch
DTE Data Terminal Equipment
Select End
IA5 International 5 Number
NN National Number
Network Terminal Number
4DTE/DCE Physical Interface Elements
GB/T11593—2001
4.1 Electrical Characteristics
4.1.1 The electrical characteristics of the interface interchange circuit on the DCE side with a data signal rate equal to or lower than 9600bit/s shall comply with the provisions of the GB/T7619 standard without cable termination load, and the electrical characteristics of the interface interchange circuit on the DTE side shall comply with the provisions of the GB/T7619 standard with or without cable termination load, or comply with the provisions of the GB/T7618 standard. The receiver terminal B of the DTE that complies with the GB/T7618 standard must be connected to the respective interface, and the B terminals shall not be connected together (see 4.2). Note: In some cases where both ends of the interface comply with the provisions of GB/T7619 standard, in order to ensure the normal operation of the circuit, it may be necessary to add series matching resistors or cable parallel termination resistors in accordance with the provisions of GB/T7619 standard. 4.1.2 The electrical characteristics of the interface interchange circuit on the DCE side and the DTE side with a data signal rate higher than 9600bit/s shall comply with the provisions of GB/T7619 standard with or without cable termination load.
4.2 Mechanical characteristics
For mechanical arrangements, refer to ISO4903 standard (15-pin DTE/DCE interface connector and pin number allocation). 4.3 Functional characteristics of interchange circuits
X.24 recommendation gives the definition of interchange circuits (see Table 1). In this standard, the signal states of interchange circuits T, C, R and I are represented by t, C, r and i respectively. The signals of circuits C (control) and I (indication) have two states: continuous conduction\ON\ (valid level of binary 0) and continuous disconnection\OFF\ (valid level of binary 1).
Interchange circuit
Signal ground or common return
Common return of DTE
To DCE
From DCE
Interchange circuit
Signal symbol timing
Byte timing
DTE signal symbol timing
GB/T11593—2001
Table 1 (end)
To DCE
From DCE
This conductor can be used to reduce environmental signal interference at the interface. When using shielded interconnection cable, more connection considerations are specified in the X.24 recommendation and ISO4903 standard.
2 Provides timing for continuous isochronous data transmission. 3 Provides optional additional service facilities (see 5.1.1). 4 How the DCE uses and terminates this circuit is at the discretion of the network management department. 4.4 Physical Link Control States
When circuit C or I is in the relevant state, the DTE and DCE shall be prepared to send at least 24 bits of continuous binary 0 and 1 on circuit T or R. When circuit I or C is in the relevant state, the DTE or DCE shall consider it as a stable state when 16 bits of continuous 0 or 16 bits of continuous 1 are detected on circuit R or T.
If the DTE (or DCE) recognizes that the equipment on the other side of the interface circuit is sending a signal identifying the current state, the DTE (or DCE) may start sending the signal of the next valid state. If the DTE (or DCE) is not ready to start sending the signal of the next valid state, it must continue to send the current state signal. NOTE: As for state 12, the description of 7.1 is more important than 4.4. 4.5 Quiescent Phase
During the quiet phase, the DTE and DCE may send signals to each other to enter the working phase, such as the call control phase or data transfer phase specified in the corresponding service. At the interface, the basic static signals of DTE and DCE appearing in various combinations represent different interface states as defined below, see Figure A1.
4.5.1 DTE static signals
4.5.1.1 DTE ready
DTE sends a signal of t=1, C=OFF according to the corresponding service, indicating that it is ready to enter the working phase. 4.5.1.2 DTE uncontrollably not ready
Usually due to abnormal working conditions of DTE, it sends a signal of t=OC=OFF according to the corresponding service, indicating that it cannot enter the working phase.
For point-to-point leased circuit services, when DTE enters "DTE uncontrollable not ready", the remote interface can send a signal of r=0, i=OFF. Other actions taken by DCE are to be determined. For centralized multipoint leased circuit services, when a DTE enters "DTE uncontrollable not ready", this signal will not be indicated at the interface of other connected DTEDCE. 4.5.1.3 DTE controllable not ready
"DTE controllable not ready" means that although the DTE is working, it is temporarily unable to accept circuit switching services. Incoming call. The use of "DTE controllable not ready" for other services is to be determined. This signal is represented by t=01 (alternating bits 0 and 1), c=OFF, and the signal duration is at least 24-bit time interval. Note: As defined in 4.5.3.1, "DTE controllable not ready" is usually entered from the "ready" state. In some networks, if the DTE does not first send the "DTE ready\ signal when the DCE sends the "DCE ready", the DCE may not recognize the "DTE controllable not ready" signal.
4.5.2DCE static signal
4.5.2.1DCE ready
DCE sends the signal r=1, i=OFF according to the corresponding service, indicating that it is ready to enter the working phase. 3
4.5.2.2DCE not ready
GB/T11593—2001
“DCE not ready” means that no service can be used. When the network fails or the test loop is activated, this status signal should be sent as much as possible. This signal is represented by r=0, i=OFF. 4.5.2.3DCE controllable not ready
“DCE controllable not ready” means that the DCE is working but cannot provide services temporarily. This signal is represented by r=01.. (alternating bits 0 and 1), i=OFF, and the signal duration is at least 24bit time interval. NOTE
1 "DCE controllable not ready" can be entered from any state. 2 "DCE controllable not ready" can be used as an optional service facility. 4.5.3 Static state (see Figure A1)
4.5.3.1 Ready (state 1)
When DTE and DCE send "DTE ready" and "DCE ready" respectively at the same time, enter "Ready to go" (state 1). 4.5.3.2 State 14
When DTE and DCE send "DTE controllable not ready" and \DCE ready\ respectively at the same time, enter state 14. 4.5.3.3 State 18
When DTE and DCE send "DTE controllable not ready" and \DCE ready\ respectively at the same time, enter state 18. 4.5.3.4 State 22
When DTE and DCE send "DTE uncontrollable not ready" and "DCE not ready" respectively at the same time, it enters state 22. 4.5.3.5 State 23
When DTE and DCE send "DTE controllable not ready" and "DCE not ready" respectively at the same time, it enters state 23. 4.5.3.6 State 24
When DTE and DCE send "DTE uncontrollable not ready" and "DCE ready" respectively at the same time, it enters state 24. 4.6 Fault Detection
4.6.1 Fault status of interchange circuits (see Note) Note: The relationship between receiver circuit fault detection and specific interchange circuits according to the type of fault detection is shown in Chapter 11 of GB/T7618-1987 and Chapter 9 of GB/T7619-1987.
DTE uses type 2 fault detection and interprets the fault status on circuit R as r=0. Using type 1 fault detection, the fault status on circuit I is interpreted as i=OFF. And the fault status on both circuits R and I is interpreted as r=0, c=OFF, that is, "DCE is not ready". Or using Type 3 fault detection, DTE interprets the fault status of circuit R or I as "DCE is not ready", that is, r=0, i=OFF.
DCE uses Type 2 fault detection and interprets the fault status on circuit T as t=0. Using Type 1 fault detection, the fault status on circuit C is interpreted as c=OFF. And the fault status on circuits T and C is interpreted as t=O, c=OFF, that is, "DTE is uncontrollable and not ready". Or using Type 3 fault detection, DCE interprets the fault status of circuit T or C as "DTE is uncontrollable and not ready", that is, 1=0, c=OFF.
4.6.2DCE Failure Status
If the service cannot be provided to DCE for a predetermined time (for example, the synchronization signal is lost or the call line signal is lost), it sends a signal r=0, i=OFF to indicate "DCE is not ready" (see 84.5.2.2). This predetermined time depends on the network. Before the DCE sends the "DCE is not ready" signal, when i=ON, the DTE receives a chaotic signal or continuous binary 1 on circuit R. 4.6.3 Signal Code Element Timing Provisions
At any time, even when the DCE synchronization signal or the call line signal is lost, the signal code element timing signal must be transmitted to the DTE through circuit S. The signal code element timing rate deviation The difference must not be greater than ±1% of the standard value. 5 Synchronization and error checking of call control characters GB/T11593-2001
All characters used for call control are selected from the International 5 Number (IA5) recommended by T.50. 5.1 Character synchronization
In order to exchange call control information between DTE and DCE, correct character synchronization must be established. Each call control character sequence sent to and from DCE must be preceded by at least two consecutive characters 1/6 (SYN). 5.1.1 Some network administrations require DTE to synchronize the call control characters it sends according to the character SYN transmitted to it or the signal on the byte timing interchange circuit.
Network administrations that require this synchronization The competent authority shall provide byte timing interchange circuits, but the use of byte timing interchange circuits by the DTE is not specified. 5.1.2 Some network competent authorities allow the call control characters sent by the DTE to be independent of the character SYN transmitted to it. 5.1.3 In addition, during a transition period (see note), the network competent authority shall provide a connection between the DTE and the public data network that operates as described in 5.1.2.
Note: The length of this transition period shall be determined according to user requirements and other relevant factors clarified by each network competent authority. 5.2 Error checking
According to the provisions of Recommendation X.4, the IA5 characters used for call control exchanges use odd parity. 6 Elements of the call control stage in circuit switching services The state diagram of Figure A2 shows the following. The relationship between the states of the "call control" phase defined above is also shown. The transactions recognized between these states under normal operating conditions are also shown. Figures B1 and B2 give examples of the time sequence between these states and the related timeout operations.
Entry into and exit from the various states represented by IA5 characters on circuits T and R must be carried out on character boundaries. At present, some networks do not restrict the transition from state 6 to state 11 or from state 6 to state 12 on character boundaries. Once the DCE has achieved character synchronization in response to a call request or to provide a personal call, synchronization must be maintained until the transition to state 11 "connection in progress". If state 11 is skipped, this synchronization is maintained until "data transmission ready". This means that all character sequences of the IA5 code sent on circuit R, such as character 2/11 (\+\), "call in progress" signal, "information provided by DCE" signal, etc., are on the same character boundary, even if they are separated by two or more characters SYN. The call control phase may be terminated by the DTE or DCE in accordance with the "clear" specified in Chapter 8. 6.1 Events in the call control procedure (see Figure A2) 6.1.1 Call request (state 2)
After the calling DTE sends the "DTE ready" signal, it may send a continuous binary signal t=0, c=ON to indicate a call request. The transition from the "ready" state (t=1, c=OFF) to the "call request" state (t=0, c=ON) must be such that the transition from c=ON to t=0 is a maximum time interval of 7 bits. Either circuit C or T may start the transition first. NOTE: In the case of the best use of byte timing circuit B, the transitions from =0 and c=ON shall occur within the same bit time interval. This may be a requirement for the use of special user service facilities (to be studied in the future). If the DTE sends the "call request" (state 2) signal at the same time as the DCE sends the signal r-0, i=OFF, the DCE is considered to be in state 19 ("DCE clear indication\).
6.1.2 Start selection (state 3)
When the network is ready to receive selection information, DCE sends i=OFF, first sends two or more consecutive characters 1/6 (\SYN\) on circuit R, and then sends consecutive word lines 2/11 ("+\". The "Start selection\" state is maintained until the "end of selection" signal is received, or in the case of "direct call", until the "DTE wait\" signal is received.
The "Start selection" signal should be sent within 3s of issuing a "call request". 6.1.3 Selection signal sequence (state 4)
GB/T11593—2001
When c=ON, DTE sends the "selection" signal sequence through circuit T, and at least two consecutive characters 1/6 (\SYN\) must be sent at the beginning of the sequence.
The "selection" signal sequence The format of the column is specified in 6.6.1. The information content and encoding of the "Select" signal sequence are specified in Appendix G and Recommendation X.121. The "Select\ signal sequence shall start within 6 seconds of receiving the "Start Select" signal and end within 36 seconds. The maximum time interval allowed between each select character is 6 seconds. If there is a time interval between each select character, it shall be filled with the character 1/6 (\SYN\) (in this case c=ON). 6.1.4 DTE Wait (State 5)
During the "DTE Wait" period, the DTE sends a continuous binary status signal t=1, c=ON (see 6.4\Direct Call\ state). 6.1.5 Incoming call (State 8)
The DCE sends i=OFF and sends two or more consecutive characters 1/6 (\SYN") and then 0/7 ("BEL") through circuit R to indicate a human call. bzxz.net
If DCE sends the "personal call" signal and DTE sends the t=0c=OFF signal at the same time, the DTE is considered to be in state 16 ("clear request").
When DTE sends "DTE uncontrollable not ready" or "DTE controllable not ready", the connection of human call is prohibited. 6.1.6 Call Acceptance (State 9)
6.1.6.1 Overview
When DTE sends a continuous binary signal t=1, c=ON, it means that DTE accepts human call. 1) If the human call is not accepted within 500ms, DCE will return to the "DCE ready" state. 2) If manual answering is allowed, if the human call is not accepted within 60s, DCE will return to the "DCE ready" state. 6.1.6.2 Subaddressing
Subaddressing is an optional procedure.
Two subaddressing procedures are defined on the called side: simple subaddressing procedure and enhanced subaddressing procedure. The choice of these procedure clauses is at the discretion of each network administration.
6.1.6.2.1 Simple subaddressing procedure (see Figure A6) This procedure is as follows:
1) "Call accepted", see 6.1, 6.1. 2) "DCE waiting", see 6.1.7.
3) "DCE provided information", if provided, after the DTE sends the "Call accepted" message, the DCE sends the subaddressing information to the called DTE before other "DCE provided information" (if any). The format of the subaddressing information is defined in 6.6.3. The content of the subaddressing information is defined in Appendix H. 4) "Connection in progress", see 6.1.10.
5) "Data transmission ready", see 6.1.11. 6.1.6.2.2 Enhanced sub-addressing procedures (see Figures A5 and B3) 6.1.6.2.2.1 Continue Call Information (State 9B) Note: State 9B can only be entered when the DTE has sub-addressing procedures. - When the DTE issues c=OFF and sends two or more consecutive characters 1/6 ("SYN") on circuit T, and then sends characters 2/10 ("*\") continuously, it indicates that the DTE accepts the incoming call. Within 500ms of receiving the "incoming call" signal, it should start sending the "continue call information" and stop sending it after receiving the "end call information".
6.1.6.2.2.2 Call Information Signal Sequence (State 10C) Note: State 10C can only be entered when the DTE has sub-addressing procedures. 6
GB/T11593-2001
When i=OFF, the DCE sends the "call information" signal sequence through circuit R, and the sequence appears on the character boundary as when entering state 8.
The "call information" signal can be preceded by two or more consecutive characters 1/6 (SYN\). "Call information" is also a kind of "DCE provided information" (see 6.1.9). The information content and encoding of the "call information" signal sequence are shown in Appendix H and Recommendation X.121. Within 2 periods after sending the "continue call information\", the "call information" signal sequence starts to be sent and completed. If there is a maximum time interval between each call information character, the word 1/6 (\SYN) should be used to fill it (in this case 1=OFF).
The format of the "call information" is the same as the format of the "DCE provided information" and is specified in 6.6.3. 6.1.6.2.2.3DCE wait (state 6D and 6C) During the \DCE wait\ period, the DCE sends two or more consecutive characters 1/6 (\SYN\) and sends i=OFF. 6.1.6.2.2.4 DTE provided information (state 25) A DTE with subaddressing procedures sends c=OFF and sends "DTE provided information" on circuit T. "DTE provided information" consists of one or more "DTE provided information" blocks, and the maximum length of each "DTE provided information" block is 128 characters.
Note: The maximum length value of 128 characters is tentative and may be changed to other values ​​in the future. The format of "DTE provided information" is defined in 6.6.4. The encoding of "DTE provided information" shall comply with Appendix F and Recommendation X.96. "DTE provided information" is sent on character boundaries as when entering state 9B. Each "DTE provided information" block can be separated by character 1/6 (\SYN\).
The "DTE provided information" (state 25) should be sent to the DCE within 20 seconds after receiving the "end call information" signal character 2/11 (\+").
After receiving the \information\block provided by the DTE, the DCE shall reset and restart the timeout counter T14C. 6.1.7 DCE wait (state 6A and state 6B) During the "DCE wait" period, the DCE shall send i=OFF and send two or more consecutive characters 1/6 (\SYN") on circuit R. In state diagram A2, state 6A is used for the calling procedure and state 6B is used for the called procedure. 6.1.8 Call progress signal (state 7)
When the network encounters the appropriate state, the DCE sends the "Call Progress" signal and i=OFF signal to the calling DTE on circuit R. A "Call Progress" signal sequence consists of one or more "Call Progress" signal blocks, and a "Call Progress" signal block consists of one or more "Call Progress" signals.
The format of the "Call Progress" signal sequence is defined in 6.6.2. The encoding of the "Call Progress" signal is given in Appendix F. The description of the "Call Progress" signal is given in Recommendation X.96. The "Call Proceeding" signal is preceded by at least two consecutive characters 1/6 (\SYN\), which are sent in state 6A. The time interval between these blocks is also filled with "DCE Wait" (state 6A). The DCE sends the "Call Proceeding" signal within 20s after the "Selection End" signal, or within 20s after the DTE sends the "DTE Wait" signal in the case of "Direct Call". However, the DCE will not send the "Call Proceeding" signal before receiving the "Selection End" signal or before the DTE sends the "DTE Wait" signal. The exception is that when the T11, T12 or T13 timeout counter expires, the "Call Proceeding" signal may be sent, followed by a "Clear Indication". Note: When errors are detected in the received "Call Proceeding" signal sequence, the DTE may not process these signals or call again after clearing. 6.1.9 Information provided by DCE (states 10A and 10B) DCE sends i=OFF and sends "information provided by DCE\ to the calling DTE (state 10A) or the called DTE (state 10B) through circuit R.
GB/T11593-—2001
"Information provided by DCE" consists of one or more "information provided by DCE" blocks, and the maximum length of each block is limited to 128 characters. The format of "information provided by DCE" is defined in 6.6.3. The content of "information provided by DCE" is given in Appendix H. "Information provided by DCE\ is preceded by at least two consecutive characters 1/6 (\SYN"). The "DCE provided information" block is separated by more than one character 1/6 (SYN) (the time interval between each block is filled with two or more characters SYN, to be determined). In the case of the calling DTE (state 10A), the leading character SYN and the separating character SYN are issued when "DCE waits" (state 6A). In the case of the called DTE (state 10B), the leading character SYN and the separating character SYN are issued when "DCE waits" (state 6B). In some cases, the character SYN can be inserted between the characters in the "DCE provided information" block. At least two characters SYN are inserted each time, and these inserted characters should be counted within the maximum length of 128 characters per block. In short, the number of inserted characters and the number of inserted characters SYN should be as small as possible.
The "DCE provided information" sequence (state 10B) should be sent to the called DTE within 6s of the "call accepted" signal. After the called DTE receives the "DCE provided information" block, it should reset the time limit counter T4B. 6.1.9.1 Line Identification
“Calling and called line identification” is an optional additional service facility. The information content of “Calling and called line identification” is given in Appendix H. "Calling Line Identification" and "Called Line Identification" are sent by DCE via circuit R during state 10B or 10A respectively, and i-OFF signal is sent at the same time.
When providing this service, DCE shall send "Called Line Identification" (state 10A) signal to the calling DTE after sending all "Call Proceeding" signals.
When providing this service, DCE shall send "Calling Line Identification" (state 10B) signal to the called DTE after DTE sends "Call Accepted" signal.
When the calling network does not provide "Calling Line Identification" service facilities, or when the current network does not provide "Called Line Identification" service facilities, DCE shall provide "virtual line identification" to DTE. In some networks, when the calling network does not provide "Calling Line Identification", DCE provides DTE with data network identification code (DVIC) to replace the "virtual line identification". 6.1.9.2 Accounting Information
"Accounting Information" is an optional additional service facility provided during state 10B. After the call requesting "Accounting Information" is cleared, the DCE establishes a human call to the DTE during the 200ms after entering the "Ready" state (state 1) to provide "Accounting Information". Note: It is recommended that the DTE does not send a "Call Request" or "Not Ready" signal during the above 200ms, otherwise the DCE does not send "Accounting Information" to the DTE. The DCE sends the "Accounting Information" through circuit R and sends the i=OFF signal. The DCE sends a "Clear Indication" (state 19) after sending the last "Accounting Information" block. If the DCE does not send a "Clear Indication" before this, the DTE should send a Clear Request" (state 16) after correctly receiving the "Accounting Information" signal. The format of "Accounting Information" is defined in 6.6.3. 6.1.10 Connection in Progress (State 11)
When making a connection, the DCE sends a signal r=1, i=OFF to indicate "Connection in Progress" (State 11). Sometimes, the "Connection in Progress" state 11 can be skipped.6.1.11 Data transmission ready (state 12) For data transmission between two DTEs, when the connection is valid, DCE sends a signal of r=1, i=ON to indicate "data transmission ready" (state 12).
1) Within 6s after DTE receives the last "call progress" signal or the information signal provided by DCE, or within 20s after DTE sends the "selection end" signal, DCE indicates "data transmission ready" to the calling DTE. 2) When the called DTE is allowed to answer manually, within 60s after DTE receives the corresponding "call progress" signal, or within 20s after DCE receives the "selection end" signal, DCE indicates "data transmission ready" to the calling DTE. 8
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