GB/T 11599-1989 Use of data terminal equipment (DTE) for interface with synchronous V-series modems on public data networks
Some standard content:
National Standard of the People's Republic of China
GB/T11599—1989
Use on public data networks ofdata terminal equipment (DTE) which is designed for interfacingtosynchronous V-series MODEMS Issued on August 21, 1989
State Administration of Technical Supervision
Implementation on March 1, 1990
National Standard of the People's Republic of China
Use on public data networks ofdata terminal equipment (DTE) which is designed for interfacingtosynchronous V-series MODEMS
This standard equivalently adopts cCITT Recommendation X.21bis. GB/T11599—1989
This standard is the usage of data terminal equipment (DTE) originally designed to interface with synchronous V-series modems when accessing the public data network in my country when the public data network is opened. This standard is equivalent to the English version of X.21bis (1984) recommended by cCITT. This standard takes into account:
The interface between data terminal equipment (DTE) and data circuit terminal equipment (DCE) working synchronously on the public data network has been specified in GB11593-89.
Some telecommunications management departments are planning to connect the synchronous DTE originally designed to interface with synchronous V-series modems to the public data network as a transitional measure.
Therefore, it is stipulated that:
DTE with V-series interface can be connected to the public data network by: a. Leased circuit service (point-to-point and centralized control multipoint); b. Direct calling facility;
c. Addressed calling facility.
This recommendation specifies the mode of operation and optional performance when data circuits are interconnected with V-series DTE. The interoperability between V-series DTE and GB11593-89 DTE is described in Appendix A. 1 Use of V-series DTE for leased circuit services and packet switching services (GB1159589 Class 1) 1.1 Overview
The use of V-series DTE for leased circuit services on public data networks is discussed below. The data signal rate is the rate for the user service type using synchronous transmission specified in GB11589-89. 1.2 Use of interchange circuits
The electrical characteristics of the interchange circuits on the DCE side and the DTE side of the interface may conform to GB3455-82, which uses the 25-pin connector and pin assignment specified by GB6107-85, or it may conform to GB7618-87, which uses the 37-pin connector and pin assignment specified by GB995088. The telecommunications administration department may choose to provide only one of the interfaces. In the case where the telecommunications administration department allows the interconnection of GB3455-82 equipment (one side of the interface) and GB7618-87 equipment (the other side of the interface), reference should be made to GB7618-87 and GB9950-88 [ISO4902) standards (the supplier of GB7618-87 equipment is responsible for providing the adapter required for interconnection with GB3455-82 equipment). For applications with a data signal rate of 48 kbit/s, the connectors and electrical characteristics on the DCE side and the DTE side of the interface are given in GB9951-88 (pin assignment of 34-pin interface connector) and GB9412-88, respectively. Another option for the 48 kbit/s data signal rate is that the connectors and electrical characteristics on the DCE side and DTE side of the interface can be GB9950-88 (ISO4902) and GB7618-87/GB761987 respectively, as with GB9412-88. The latter option configuration cannot interconnect with GB9951-88 and GB9412-88 configurations. Telecommunications management departments may decide to provide only one of the interface options at 48 kbit/s.
Table 1 Usage of interchange circuits for leased circuit services. Table 1
Circuit number
Signal ground or common return
Send data
Receive data
Request to send
Ready to send
Data equipment ready 1
Connect data equipment to line 28)
Data channel receive line signal detector
Transmitter signal symbol timing (DCE)
Receiver signal symbol timing (DCE))
Loopback/maintenance test 5)
Local loopback 5
Test indicator (DCE)
Note: 1) Circuit 107 enters the disconnected state only if the DCE loses power (usually interpreting the indeterminate state as disconnected), loses service (see description in 3.2 below) or circuit 108/1 (when provided) goes disconnected. 2) This circuit is not required for GB9412 compatible interfaces. 3) When circuit 108/1 is provided, DCE interprets the on state on this circuit as indicating that the DTE is operating. If circuit 108/1 is not provided, DCE shall treat the missing circuit 108/1 as on state. When circuit 108/1 (when provided) is on state and the circuit connection is available, DCE turns circuit 107 to on state.
4) DCE shall provide transmitter and receiver signal symbol timing to DTE; this is achieved by feeding the timing signal from DCE to circuits 114 and 115.
5) This circuit is not required in networks that do not provide automatic loop action. The functions of all these circuits comply with GB3454-82 and the corresponding modem recommendations (see 1.2.1 below). 1.2.1 Working requirements
1.2.1.1 Half-duplex operation
In principle, the data circuits provided have duplex transmission capabilities. However, when circuit 105 is required to respond remotely to circuit 109, this may be provided on an optional basis (see Appendix A). NOTE: It should be noted that although circuit 105 can control circuit 109 at the other end, in the case of a half-duplex facility, the detection of the line signal should be replaced by some other control mechanism.
1.2.1.2 Response time
As a response to the disconnection and connection of circuit 105, the response time of circuit 106 from disconnection to connection should be between 30ms and 50ms for a user rate of 600bit/s2
GB/T11599—1989
tentatively set between 30ms and 50ms for a higher user rate, and between 10ms and 20ms for a higher user rate. 1.2.1.3 Clamping
The following situations apply:
a. In the event of a line fault (e.g., channel out of service, loss of alignment), the DCE shall clamp circuit 104 to a stable binary 1 state and circuit 109 to an open state;
b. In all applications, when circuit 109 is in the open state, the DCE shall maintain circuit 104 in the binary 1 state, c. In addition, when half-duplex facilities are provided, the DCE shall maintain circuit 104 in the binary 1 state and circuit 109 in the open state when circuit 105 is in the connected state;
d. When circuit 105 or circuit 106 or both are in the open state, the DTE shall maintain circuit 103 in the binary 1 state. 1.2.1.4 Timing Arrangements
When the DCE has the capability to generate timing signals, timing signals shall always be provided on circuits 114 and 115, regardless of the state of the other circuits. When the DCE is unable to generate timing information, circuits 114 and 115 shall be maintained in the open state by the DCE. 2. Usage of V-series DTE for direct calling and addressed calling facilities 2.1 Overview
The following discusses the usage of V-series DTE for direct calling and addressed calling facilities in public data networks. The data signal rate is in accordance with the rate of the user service type using synchronous transmission specified in GB11589-1989. 2.2 Usage of Interchange Circuits
The electrical characteristics of the interchange circuits on the DCE side and the DTE side of the interface may conform to GB3455-82, which uses the 25-pin connector and pin assignments specified by the GB6107-85 standard, or may conform to GB7618--87, which uses the 37-pin connector and pin assignments specified by the GB9950-88 standard. The telecommunications administration may choose to provide only one of the interfaces. In situations where the telecommunications administration permits the interconnection of GB3455-82 equipment (on one side of the interface) and GB7618-87 equipment (on the other side of the interface), reference should be made to the GB7618-87 and GB9950-88 standards (the supplier of GB7618-87 equipment is responsible for providing the adapters required for interconnection with GB3455-82 equipment).
For applications with a data signal rate of 48 kbit/s, the connectors and electrical characteristics on the DCE side and DTE side of the interface are given in GB9951-88 (pin assignments for 34-pin interface connectors) and GB9412-88, respectively. Another option for a data signal rate of 48 kbit/s is that the connectors and electrical characteristics on the DCE side and DTE side of the interface may be in GB9950-88 and GB7618-87/GB7619-87, respectively, as with GB9412-88. The latter option cannot interconnect with the GB9951-88 and GB9412-87 configurations. Telecommunications administrations may decide to provide only one of the interface options at 48 kbit/s. Table 2 gives the interchange circuits.
GB3454—82
Interchange circuit code
108/1 or
Signal ground or common return line
Send data
Receive data
Request data
Ready to send
Data equipment is ready
Connect data equipment to line
Data terminal is ready
Data channel receiving signal detector
GB3454 —82
Switching Circuit Code
GB/T11599—1989
Continued Table 2
Transmitter Signal Symbol Timing (DCE)
Receiver Signal Symbol Timing DCE)
Call Indicator
Local Loopback
Test Indicator
For further definitions of the interchange circuits outlined below, refer to GB3454-82 and the corresponding V-series modem standards. 2.2.1 Call Setup and Teardown Phase
The following interchange circuits shall be used as control signals during the call setup and teardown phases: a signal ground or common return,
Circuit 102—
Circuit 107—Data Equipment Ready;
This circuit is used to indicate the following operating functions. Table 3
State of circuit 107
ON
OFF
OFF
Function
(See 2.2.1.1)
Data ready
DCE clear indication
DCE clear confirmation
Note: In duplex transmission, when the DTE does not use circuit 105, circuit 106 is placed in the on state after a delay of 0 to 20 ms relative to the transition of circuit 107 to on.
Circuit 108/1 - Connect data equipment to the line. This circuit is used instead of circuit 108/2. The following operating functions should be indicated. Table 4
State of circuit 108/1
ON
ON
OFF
OFF
Function in network (see clause 2.2.1.1)
Call request
Call accepted
DTE clear request
DTE clear confirm
Note: This circuit should not operate when the DTE is connected to a modem that does not terminate circuit 108/1. Circuit 108/2
A data terminal is ready,
This circuit is used instead of circuit 108/1 and should indicate the following operating functions. Table 5
State of circuit 108/2
ON
OFF
OFF
Function in the network (see clause 2.2.1.1)Call acceptance
DTE clear request
DTE clear confirmation
GB/T11599—1989
Note: This circuit should not operate when the DTE is connected to a modem that does not terminate circuit 108/2. Circuit 114—Transmitter signal symbol timing (DCE); Circuit 115—Receiver signal symbol timing (DCE); The DCE should provide the DTE transmitter and receiver signal symbol timing by feeding the timing signal from the DCE to circuits 114 and 115.
Circuit 125 - Call indicator;
The connected state indicates an incoming call. This circuit is to be turned off under the following conditions: a. When circuit 107 is turned on, or
b. DCE ready is received from the network, or c. DCE clear indication is received.
Circuit 141 - Local loopback;
The signals on this circuit are used to control the loop 3 test state in the local DCE. This circuit is not required in networks where automatic loopback action is not provided.
Circuit 142 - Test indicator;
This circuit is used to indicate to the DTE the test mode state of the DCE. 2.2.1.1 Operating requirements
2.2.1.1.1 Call request
For direct calling facilities, the DTE indicates a call request by turning circuit 108/1 on. Circuit 108/2 cannot be used for this purpose.
2.2.1.1.2 Call Acceptance
After receiving an incoming call, DTE shall turn circuit 108/1 or 108/2 from disconnected to connected within 500ms to indicate call acceptance, otherwise the call will be cleared. When DCE sends an incoming call to DTE, if DTE's circuit 108/2 is already in the connected state, DCE will regard the connected state on circuit 108/2 as a call connected indication. Alternatively, when DTE does not provide circuit 108/1 or 108/2, DCE shall generate a call acceptance signal to the network as a response to the incoming call signal from the network. A DTE controllable unready signal can also be sent to the network by manual operation on DCE.
2.2.1.1.3 DCE Clear Indication/DTE Clear Confirmation By turning circuit 107 disconnected, DCE transmits the clear indication to DTE. When DTE clear confirmation is provided, the DTE shall give a DTE clear confirmation signal by turning circuit 108/1 or 108/2 off within 100ms after the DCE clear indication is issued on circuit 107. Otherwise, the DCE may consider the DTE to be in an uncontrollable unready state before 108/1 or 108/2 is turned off, or before the DCE is manually operated to generate a ready signal. Circuit 108/1 should always be able to give a DTE clear confirmation. Alternatively, when the DTE does not turn circuit 108/2 off as a DTE clear confirmation, a clear confirmation will be automatically generated in the DCE as a response to receiving a clear indication from the network, and the DTE is considered to be in a ready state. In the case where the DTE expects circuit 107 to be disconnected only as a response to the disconnection of circuits 108/1 or 108/2, in this case, the DCE will not turn circuit 107 off as a DCE clear indication, and in this case, the DCE clear indication is not transmitted to the DTE through the interface. At this time, the required DTE clear confirmation signal should be automatically generated in the DCE and used as a response to the clear indication signal received from the network. Before circuit 108/1 or 108/2 is disconnected, the DTE can be considered to be in an uncontrollable and unready state. 2.2.1.1.4 Line identification
V series DTE cannot process calling and called identification signals. 2.2.1.1.5 Call progress signal
V series DTE cannot process call progress signals. If automatic addressing calls are provided in accordance with GB762387, the reception of a negative call progress signal will be indicated to the DTE on circuit 205. 5
2.2.2 Data transfer phase
GB/T11599—1989
The interchange circuits shown in Table 6 shall be used in the data transfer phase. Table 6
GB3454—82
Interchange circuit number
Signal ground or common return
Send data
Receive data
Request to send
Ready to send
Data channel receive line signal detector
Transmitter signal symbol timing (DCE) (see note) Receiver signal symbol timing (DCE) (see note) Note: DCE shall provide transmitter and receiver signal symbol timing to DTE, which is achieved by feeding the timing signal from DCE to circuits 114 and 115.
The functions of all these circuits comply with GB3454 and the corresponding modem recommendations. 2.2.2.1 Operating Requirements
2.2.2.1.1 Half-Duplex Operation
In principle, the data circuits provided shall have duplex transmission capability. However, this may be provided on an optional basis when circuit 105 is required to provide remote response to circuit 109 (see Appendix A). 2.2.2.1.2 Response Time
The response time of circuit 106 from disconnection to connection in response to circuit 105 from disconnection to connection shall be tentatively between 30 ms and 50 ms for a user rate of 600 bit/s and between 10 ms and 20 ms for higher user rates. 2.2.2.1.3 Clamping
Applies in the following cases:
a: In the event of a line fault (e.g. channel out of service, loss of alignment) the DCE shall clamp circuit 104 to a stable binary 1 state and circuit 109 to an open state,
b. In all applications, the DCE shall maintain circuit 104 in the binary 1 state when circuit 109 is in the open state;
c. In addition, when half-duplex facilities are provided, the DCE shall maintain circuit 104 in the binary 1 state and circuit 109 in the open state when circuit 105 is in the connected state;
d. When circuit 105 or circuit 106 or both are in the open state, the DTE shall maintain circuit 103 in the binary 1 state. 2.2.2.1.4 Timing Arrangement
When the DCE has the capability to generate timing signals, timing signals shall always be provided on circuits 114 and 115, regardless of the state of the other circuits. When DCE cannot generate timing signals, circuits 114 and 115 should be kept in the disconnected state by DCE. Continuous isochronous operation should be adopted.
2.3 Mode of operation
2.3.1 Direct calling facility
The following modes of operation can be provided:
a. Automatic direct calling and automatic disconnection of DTE, circuit 108/1 should be used. Manual disconnection from DCE should not be used in this case,
b. Manual direct calling of DCE and automatic disconnection of DTE, circuit 108/26 should be used
GB/T11599—1989
c. Manual direct calling and manual disconnection of DCE: used for DTE that is not provided with circuit 108 or DTE that cannot be disconnected using circuit 108/2.
Only automatic call answering controlled by circuit 108/1 or 108/2 (when provided) or automatically controlled within the DCE itself shall be implemented. However, in the latter case, a DTE controllable not ready signal may be issued to the network by manual action at the DCE. NOTE: Considerations for manual answering and the implications of manual DTE clearing confirmation are for further study. 2.3.2 Addressed Calling Facilities
The following modes of operation may be provided:
a. Manually addressed calling by the DCE and automatic disconnection of the DTE shall use circuit 108/2; b. Manually addressed calling by the DCE and manual disconnection for DTEs that are not provided with circuit 108/1 or 108/2 or that cannot be disconnected using circuit 108/2.
Only automatic call answering controlled by circuit 108/2 (when provided) or automatically controlled within the DCE itself shall be implemented. However, in the latter case, a DTE controllable unready signal may be sent to the network through manual action on the DCE; c. If DTE automatic addressing calls and automatic disconnection are provided, the 200 series interchange circuits and the relevant procedures of GB7623 should be used. The spare and code positions on the digital signal circuits 206 to 209 can be used for specific purposes during the selection sequence of the public data network. The relationship between the control characters on circuits 206 to 209 and the control characters of GB11593 is shown in Table 7. Table 7
Control status
In the transition period, the telecommunications management department can provide the relationship shown in Table 8. Table 8
Control state
3 Fault detection and isolation
3.1 Uncertain state on interchange circuits
Corresponds to the
Control characters of GB11593-89
Corresponds to the
Control characters of GB11593-89
If the DTE or DCE cannot determine the state of circuits 105, 107, 108/1 or 108/2 and possibly circuits 103 and 104, it shall interpret it as an open state or binary 1 state (circuits 103 and 104) as specified in the relevant electrical interface specifications. 3.2 DCE fault state
If the DCE cannot provide service within a specified time (for example, loss of signal alignment or incoming line signal), it shall convert circuit 107 to the open state. The value of the specified time is network-dependent. In addition, once the DCE detects this condition, it turns circuit 109 to the disconnected state and puts circuit 104 in the binary 1 state. 3.3 Test loops The definition of test loops and the principle of using test loops to maintain tests are provided in the relevant standards. 3.3.1 DTE test loop - type 1 loop This loop is used as a basic test of DTE operation, looping back the send signal in the DTE for verification. The loop should be established in the DTE as close as possible to the DTE/DCE interface. When the DTE is in the loop 1 test state:
a. Connect circuit 103 to circuit 104 within the DTE; b. Circuit 103 provided to the DCE must be in the binary 1 state; c. Circuit 105 must be in the disconnected state;
d. Circuit 108/1 or 108/2 can be in the state before the test; e. If circuits 140 and 141 are provided, they must be in the disconnected state; f. The DCE continuously provides signal code element timing information on circuits 114 and 115, and the DTE does not have to use this timing information. In addition, the states of other interchange circuits are not specified, but they should allow normal operation as much as possible. Loop 1 can be established from the data transfer phase or from the idle phase. If the loop is established from the data transfer phase, then during the test, the DTE still operates like normal. The DCE can continue to deliver data to the DTE. Any errors that occur during the loop test are the responsibility of the DTE to recover. If the loop is established from the idle phase, the DTE shall continue to monitor circuit 125 in order to give priority to incoming calls over routine tests. 3.3.2 Local Test Loop - Type 3 Loops Local test loops Type 3 loops are used to test all or part of the operation of the DTE, interconnecting cabling, and local DCE, as discussed below: Loop 3 may be established in either state where permitted by national testing regulations. When used for testing leased circuits and for short-term testing, the DCE shall continue to provide the circuit with the line state existing before the test (e.g., data transfer or ready state) on the circuit-switched connection, or shall send a controlled not-ready state to the far-end DTE. Where the above is not feasible (e.g., certain cases of loop 3a) or is not required (e.g., long-term testing in circuit-switched applications), the DCE shall terminate existing calls and, if possible, send a not-ready state to the subscriber line. Manual control shall be provided at the DCE for activating the test loop. If automatic activation is provided on the loop, it shall be controlled by circuit 141. The exact arrangement of the test loop within the DCE is a matter of national choice. However, at least one of the local test loops described below shall be implemented. 3.3.2.1 Loop 3d
This loop tests the operation of the DTE, including the interconnecting cables, by returning the transmit signal to the DTE for verification. The loop is established within the local DCE, but does not include the generator and load of the interchange circuit. When the DCE is in the loop 3d test state:
a. Circuit 103 is connected to circuit 104
b. Circuit 105 is connected to circuits 106 and 109 simultaneously; Note: The DTE designer should be aware that this connection will result in one generator driving two loads in parallel. c. Circuits 107 and 142 are placed in the on state; d.The DCE continuously provides signal symbol timing information on circuits 114 and 115. The DTE must make use of this timing information. NOTE: When test loop 3d is in operation, the effective length of the interface cable is doubled. Therefore, to ensure proper operation of loop 3d, the maximum DTE/DCE interface cable length should be half the normal length appropriate for the data signal rate used. 3.3.2.2 Loop 3c
This loop is used to test the operation of the DTE, including the interconnecting cable and the DCE interchange circuit generator and load. The configuration is the same as that given for loop 3d in clause 3.3.2.1, except that circuit 103 is looped back to 104, and circuits 105 to 109 are looped back, including the interchange circuit generator and load. Circuit 106 should follow circuit 105 with the normal delay or no delay. The comments regarding interface cable length and input impedance limitations of the load are not applicable here. 3.3.2.3 Loop 3b
This loop is used to test the operation of the DTE and line coding, as well as the control logic and circuitry of the DCE. It includes all DCE circuitry except line signal conditioning circuitry (e.g., impedance matching transformers, amplifiers, equalizers, etc.). The delay between transmitted and received test data is a number of octets of time (see Note). Except for the location of the loop return point, its configuration is the same as that given for loop 3c in clause 3.3.2.2. NOTE: In some DCEs, the setting of loop 3b will cause a temporary loss of envelope alignment, causing random signals to appear on the receive interchange circuit for a period of time. This may affect the DTE test procedures. In some networks, the setting of loop 3b will cause the clearing of existing connections. 3.3.2.4 Loop 3a
This loop is used to test the operation of the DTE and DCE. The loop should include DCE working The maximum number of circuits used in the loop, in particular including line signal conditioning circuits. It will be recognized that in some cases it may be necessary to include various equipment (e.g. attenuators, equalizers or test loop converters) in the loopback path. The subscriber line is terminated appropriately during the test state of loop 3a. The delay between sending and receiving test data is a number of octets of time (see Note). Except for the location of the loop return point, its configuration is the same as that given in clause 3.3.2.3. NOTE: In some DCEs, the setting of loop 3a will cause a temporary loss of envelope alignment, causing random signals to appear on the receiving interchange circuit for a period of time. This may affect the DTE test procedures. In some networks, the setting of loop 3a will cause the clearing of existing connections. 3 .3.3 Network Test Loop - Type 2 Loop The test centre of the telecommunications administration shall use a network test loop (test loop 2) to test the operation of leased circuits or subscriber lines and all or part of the DCE as discussed below. Where permitted by national testing principles, the DTE may use loop 2 as follows: a. In the case of a circuit-switched network, test the operation of the network connection including the far-end DCE during the data transfer phase. After completion of the network loop test, it shall be possible to re-enter the data transfer phase, b. In the case of a leased circuit, test the operation of the line including the far-end DCE during the idle phase. While the test is in progress, the DCE places circuits 107 and 109 in the disconnected state, circuit 104 in the binary 1 state, and Circuit 142 is placed in the on state. The loop may be controlled manually by a switch on the DCE, or automatically by the network. The method used for controlling the loop and providing automatic control is a matter of national choice. In the case of leased circuit service, user control of the loop (if provided) shall be effected through circuit 104. In the event of a conflict between a call request and loop activation, the loop activation command shall have priority and the call request shall be abandoned. The exact means of testing the loop within the DCE is a matter of national choice. One of the following network test loops shall be implemented. 3.3.3.1 Loop 2b
This loop is used by the test centre of the telecommunications administration and/or the remote DTE to test the operation of the subscriber line and all circuits of the DCE except the interchange circuit generator and load.
When the DCE is in the loop 2b test state:
a. Connects circuit 104 to circuit 103 in the DCE;b. Connects circuit 109 to circuit 105 in the DCEc. At the interface, the DCE places circuit 104 in the binary 1 state and circuit 109 in the disconnected state, or alternatively forms an open circuit or power disconnected state on circuits 104 and 109;d. Places circuits 106, 107, and 125 to the DTE in the disconnected state;e. Places circuit 142 to the DTE in the connected statef. The DCE provides timing information on circuits 114 and 115. 3.3.3.2 Loop 2a
This loop is used by the test center of the telecommunications administration or by the remote DTE to test the operation of the subscriber line and the entire DCE. The configuration is the same as that given for loop 2b in clause 3.3.3.1, except for the location of the return point. 3.3.4 User Line Test Loop - Type 4 Loop 9
GB/T11599-1989
Telecommunications management departments provide user line test loop type 4 (loop) for line maintenance. 3.3.4.1 Loop 4a
This loop is only provided in the case of 4-wire user lines. Telecommunications management departments use loop 4a for line maintenance. When the sending and receiving line pairs are connected together, it cannot be assumed that the resulting circuit is normal. Loop 4a can be established inside the DCE or in a separate device.
When the DCE is in the loop 4a test state:
a. Circuit 104 to DTE is set to binary 1 state; b. Circuits 106, 107, 109 and 125 to DTE are in the disconnected state; c. Circuit 142 to DTE is in the connected state; d. DCE provides timing information on circuits 114 and 115. 3.3.4.2 Loop 4b
This loop is used by telecommunications authorities to test the operation of subscriber lines including line signal conditioning circuits within the DCE. When the receive and transmit circuits are connected at this point, loop 4b provides a connection that can be considered normal. However, since the DCE does not implement complete signal regeneration, there may be some loss of performance. Except for the location of the return point, its configuration is the same as that given for loop 4a in clause 3.3.4.1. 3.4 Signal Codeword Timing
Whenever possible, the signal codeword timing signal is transmitted to the DTE by circuits 114 and 115. In particular, the signal codeword timing signal is transmitted to the DTE when operating in accordance with one of the various loops described in 3.3 above or when the DCE loses alignment or loses the input line signal. During these conditions, the tolerance of the signal codeword timing should be ±1%. 10
GB/T11599—1989
Appendix A
Interconnection between DTEs conforming to GB11593-89 and this Standard (Supplement)
It should be recognized that for DTEs that do not use half-duplex operation, interconnection between a V-series DTE connected to a public data network in accordance with this Standard at one end and a DTE connected to a public data network in accordance with GB11593-89 at the other end should always be possible. Some telecommunications administrations may provide facilities to allow interconnection between DTEs conforming to GB11593-89 and DTEs conforming to this Standard using half-duplex operation. This is achieved by switching circuits C, I and circuits 109, 105 according to Figure A1 during the data transfer phase. Those administrations that do not provide such facilities shall cause the DCE of GB1159389 to send r=1,=ON (connection) signal when the DTE signal circuit 105 of this standard is disconnected. For those DTEs that do not require circuit 109 to be disconnected before the signal circuit 105 is connected, half-duplex operation will be allowed.
On (-ai
UFF IRiJF)
OFF
Additional Notes:
This standard is proposed by the Ministry of Posts and Telecommunications of the People's Republic of China. Figure A1
This standard is technically coordinated by the Data Communication Technology Research Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the 30th Institute of the Ministry of Electronics. GBH
aN GHI1. The same configuration as given in loop 3d, looping back circuits 105 to 109, including interchanging the circuit generators and loads. Circuit 106 shall follow circuit 105 with the usual delay or no delay. The comments regarding the length of the interface cable and the input impedance limitations of the load are not applicable here. 3.3.2.3 Loop 3b
This loop is used to test the operation of the DTE and line coding, as well as the control logic and circuits of the DCE. It includes all DCE circuits except line signal conditioning circuits (e.g., impedance matching transformers, amplifiers, equalizers, etc.). The delay between transmitted and received test data is a number of octets (see Note). Except for the location of the loop return point, its configuration is the same as that given for loop 3c in clause 3.3.2.2. NOTE: In some DCEs, the setting of loop 3b will cause a temporary loss of envelope alignment, causing random signals to appear on the receive interchange circuit for a period of time. This may affect the DTE test procedure. In some networks, the setting of loop 3b will cause the clearing of existing connections. 3.3.2.4 Loop 3a
This loop is used to test the operation of the DTE and DCE. The loop should include the DCE working The maximum number of circuits used in the loop, in particular including line signal conditioning circuits. It will be recognized that in some cases it may be necessary to include various equipment (e.g. attenuators, equalizers or test loop converters) in the loopback path. The subscriber line is terminated appropriately during the test state of loop 3a. The delay between sending and receiving test data is a number of octets of time (see Note). Except for the location of the loop return point, its configuration is the same as that given in clause 3.3.2.3. NOTE: In some DCEs, the setting of loop 3a will cause a temporary loss of envelope alignment, causing random signals to appear on the receiving interchange circuit for a period of time. This may affect the DTE test procedures. In some networks, the setting of loop 3a will cause the clearing of existing connections. 3 .3.3 Network Test Loop - Type 2 Loop The test centre of the telecommunications administration shall use a network test loop (test loop 2) to test the operation of leased circuits or subscriber lines and all or part of the DCE as discussed below. Where permitted by national testing principles, the DTE may use loop 2 as follows: a. In the case of a circuit-switched network, test the operation of the network connection including the far-end DCE during the data transfer phase. After completion of the network loop test, it shall be possible to re-enter the data transfer phase, b. In the case of a leased circuit, test the operation of the line including the far-end DCE during the idle phase. While the test is in progress, the DCE places circuits 107 and 109 in the disconnected state, circuit 104 in the binary 1 state, and Circuit 142 is placed in the on state. The loop may be controlled manually by a switch on the DCE, or automatically by the network. The method used for controlling the loop and providing automatic control is a matter of national choice. In the case of leased circuit service, user control of the loop (if provided) shall be effected through circuit 104. In the event of a conflict between a call request and loop activation, the loop activation command shall have priority and the call request shall be abandoned. The exact means of testing the loop within the DCE is a matter of national choice. One of the following network test loops shall be implemented. 3.3.3.1 Loop 2b
This loop is used by the test centre of the telecommunications administration and/or the remote DTE to test the operation of the subscriber line and all circuits of the DCE except the interchange circuit generator and load.
When the DCE is in the loop 2b test state:
a. Connects circuit 104 to circuit 103 in the DCE;b. Connects circuit 109 to circuit 105 in the DCEc. At the interface, the DCE places circuit 104 in the binary 1 state and circuit 109 in the disconnected state, or alternatively forms an open circuit or power disconnected state on circuits 104 and 109;d. Places circuits 106, 107, and 125 to the DTE in the disconnected state;e. Places circuit 142 to the DTE in the connected statef. The DCE provides timing information on circuits 114 and 115. 3.3.3.2 Loop 2a
This loop is used by the test center of the telecommunications administration or by the remote DTE to test the operation of the subscriber line and the entire DCE. The configuration is the same as that given for loop 2b in clause 3.3.3.1, except for the location of the return point. 3.3.4 User Line Test Loop - Type 4 Loop 9
GB/T11599-1989
Telecommunications management departments provide user line test loop type 4 (loop) for line maintenance. 3.3.4.1 Loop 4a
This loop is only provided in the case of 4-wire user lines. Telecommunications management departments use loop 4a for line maintenance. When the sending and receiving line pairs are connected together, it cannot be assumed that the resulting circuit is normal. Loop 4a can be established inside the DCE or in a separate device.
When the DCE is in the loop 4a test state:
a. Circuit 104 to DTE is set to binary 1 state; b. Circuits 106, 107, 109 and 125 to DTE are in the disconnected state; c. Circuit 142 to DTE is in the connected state; d. DCE provides timing information on circuits 114 and 115. 3.3.4.2 Loop 4b
This loop is used by telecommunications authorities to test the operation of subscriber lines including line signal conditioning circuits within the DCE. When the receive and transmit circuits are connected at this point, loop 4b provides a connection that can be considered normal. However, since the DCE does not implement complete signal regeneration, there may be some loss of performance. Except for the location of the return point, its configuration is the same as that given for loop 4a in clause 3.3.4.1. 3.4 Signal Codeword Timing
Whenever possible, the signal codeword timing signal is transmitted to the DTE by circuits 114 and 115. In particular, the signal codeword timing signal is transmitted to the DTE when operating in accordance with one of the various loops described in 3.3 above or when the DCE loses alignment or loses the input line signal. During these conditions, the tolerance of the signal codeword timing should be ±1%. 10
GB/T11599—1989
Appendix A
Interconnection between DTEs conforming to GB11593-89 and this Standard (Supplement)
It should be recognized that for DTEs that do not use half-duplex operation, interconnection between a V-series DTE connected to a public data network in accordance with this Standard at one end and a DTE connected to a public data network in accordance with GB11593-89 at the other end should always be possible. Some telecommunications administrations may provide facilities to allow interconnection between DTEs conforming to GB11593-89 and DTEs conforming to this Standard using half-duplex operation. This is achieved by switching circuits C, I and circuits 109, 105 according to Figure A1 during the data transfer phase. Those administrations that do not provide such facilities shall cause the DCE of GB1159389 to send r=1,=ON (connection) signal when the DTE signal circuit 105 of this standard is disconnected. For those DTEs that do not require circuit 109 to be disconnected before the signal circuit 105 is connected, half-duplex operation will be allowed.
On (-ai
UFF IRiJF)
OFF
Additional Notes:
This standard is proposed by the Ministry of Posts and Telecommunications of the People's Republic of China. Figure A1
This standard is technically coordinated by the Data Communication Technology Research Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the 30th Institute of the Ministry of Electronics. GBH
aN GHI1. The same configuration as given in loop 3d, looping back circuits 105 to 109, including interchanging the circuit generators and loads. Circuit 106 shall follow circuit 105 with the usual delay or no delay. The comments regarding the length of the interface cable and the input impedance limitations of the load are not applicable here. 3.3.2.3 Loop 3b
This loop is used to test the operation of the DTE and line coding, as well as the control logic and circuits of the DCE. It includes all DCE circuits except line signal conditioning circuits (e.g., impedance matching transformers, amplifiers, equalizers, etc.). The delay between transmitted and received test data is a number of octets (see Note). Except for the location of the loop return point, its configuration is the same as that given for loop 3c in clause 3.3.2.2. NOTE: In some DCEs, the setting of loop 3b will cause a temporary loss of envelope alignment, causing random signals to appear on the receive interchange circuit for a period of time. This may affect the DTE test procedure. In some networks, the setting of loop 3b will cause the clearing of existing connections. 3.3.2.4 Loop 3a
This loop is used to test the operation of the DTE and DCE. The loop should include the DCE working The maximum number of circuits used in the loop, in particular including line signal conditioning circuits. It will be recognized that in some cases it may be necessary to include various equipment (e.g. attenuators, equalizers or test loop converters) in the loopback path. The subscriber line is terminated appropriately during the test state of loop 3a. The delay between sending and receiving test data is a number of octets of time (see Note). Except for the location of the loop return point, its configuration is the same as that given in clause 3.3.2.3. NOTE: In some DCEs, the setting of loop 3a will cause a temporary loss of envelope alignment, causing random signals to appear on the receiving interchange circuit for a period of time. This may affect the DTE test procedures. In some networks, the setting of loop 3a will cause the clearing of existing connections. 3 .3.3 Network Test Loop - Type 2 Loop The test centre of the telecommunications administration shall use a network test loop (test loop 2) to test the operation of leased circuits or subscriber lines and all or part of the DCE as discussed below. Where permitted by national testing principles, the DTE may use loop 2 as follows: a. In the case of a circuit-switched network, test the operation of the network connection including the far-end DCE during the data transfer phase. After completion of the network loop test, it shall be possible to re-enter the data transfer phase, b. In the case of a leased circuit, test the operation of the line including the far-end DCE during the idle phase. While the test is in progress, the DCE places circuits 107 and 109 in the disconnected state, circuit 104 in the binary 1 state, and Circuit 142 is placed in the on state. The loop may be controlled manually by a switch on the DCE, or automatically by the network. The method used for controlling the loop and providing automatic control is a matter of national choice. In the case of leased circuit service, user control of the loop (if provided) shall be effected through circuit 104. In the event of a conflict between a call request and loop activation, the loop activation command shall have priority and the call request shall be abandoned. The exact means of testing the loop within the DCE is a matter of national choice. One of the following network test loops shall be implemented. 3.3.3.1 Loop 2b
This loop is used by the test centre of the telecommunications administration and/or the remote DTE to test the operation of the subscriber line and all circuits of the DCE except the interchange circuit generator and load.
When the DCE is in the loop 2b test state:
a. Connects circuit 104 to circuit 103 in the DCE;b. Connects circuit 109 to circuit 105 in the DCEc. At the interface, the DCE places circuit 104 in the binary 1 state and circuit 109 in the disconnected state, or alternatively forms an open circuit or power disconnected state on circuits 104 and 109;d. Places circuits 106, 107, and 125 to the DTE in the disconnected state;e. Places circuit 142 to the DTE in the connected statef. The DCE provides timing information on circuits 114 and 115. 3.3.3.2 Loop 2a
This loop is used by the test center of the telecommunications administration or by the remote DTE to test the operation of the subscriber line and the entire DCE. The configuration is the same as that given for loop 2b in clause 3.3.3.1, except for the location of the return point. 3.3.4 User Line Test Loop - Type 4 Loop 9
GB/T11599-1989
Telecommunications management departments provide user line test loop type 4 (loop) for line maintenance. 3.3.4.1 Loop 4a
This loop is only provided in the case of 4-wire user lines. Telecommunications management departments use loop 4a for line maintenance. When the sending and receiving line pairs are connected together, it cannot be assumed that the resulting circuit is normal. Loop 4a can be established inside the DCE or in a separate device.
When the DCE is in the loop 4a test state:
a. Circuit 104 to DTE is set to binary 1 state; b. Circuits 106, 107, 109 and 125 to DTE are in the disconnected state; c. Circuit 142 to DTE is in the connected state; d. DCE provides timing information on circuits 114 and 115. 3.3.4.2 Loop 4b
This loop is used by telecommunications authorities to test the operation of subscriber lines including line signal conditioning circuits within the DCE. When the receive and transmit circuits are connected at this point, loop 4b provides a connection that can be considered normal. However, since the DCE does not implement complete signal regeneration, there may be some loss of performance. Except for the location of the return point, its configuration is the same as that given for loop 4a in clause 3.3.4.1. 3.4 Signal Codeword Timing
Whenever possible, the signal codeword timing signal is transmitted to the DTE by circuits 114 and 115. In particular, the signal codeword timing signal is transmitted to the DTE when operating in accordance with one of the various loops described in 3.3 above or when the DCE loses alignment or loses the input line signal. During these conditions, the tolerance of the signal codeword timing should be ±1%. 10
GB/T11599—1989
Appendix A
Interconnection between DTEs conforming to GB11593-89 and this Standard (Supplement)
It should be recognized that for DTEs that do not use half-duplex operation, interconnection between a V-series DTE connected to a public data network in accordance with this Standard at one end and a DTE connected to a public data network in accordance with GB11593-89 at the other end should always be possible. Some telecommunications administrations may provide facilities to allow interconnection between DTEs conforming to GB11593-89 and DTEs conforming to this Standard using half-duplex operation. This is achieved by switching circuits C, I and circuits 109, 105 according to Figure A1 during the data transfer phase. Those administrations that do not provide such facilities shall cause the DCE of GB1159389 to send r=1,=ON (connection) signal when the DTE signal circuit 105 of this standard is disconnected. For those DTEs that do not require circuit 109 to be disconnected before the signal circuit 105 is connected, half-duplex operation will be allowed.
On (-ai
UFF IRiJF)
OFF
Additional Notes:
This standard is proposed by the Ministry of Posts and Telecommunications of the People's Republic of China. Figure A1
This standard is technically coordinated by the Data Communication Technology Research Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the 30th Institute of the Ministry of Electronics. GBH
aN GHI4 Loop 3a
This loop is used to test the operation of the DTE and DCE. The loop should include the maximum number of circuits used in the operation of the DCE, including, in particular, line signal conditioning circuits. It will be recognized that in some cases it may be necessary to include various devices (e.g., attenuators, equalizers, or test loop switches) in the loop path. The subscriber line is terminated appropriately during the test state of loop 3a. The delay between the transmission and reception of test data is a number of octets (see Note). The configuration is the same as given in 3.3.2.3, except for the location of the loop return point. NOTE: In some DCEs, the configuration of loop 3a will cause a temporary loss of envelope alignment, causing a period of random signals to appear on the receiving interchange circuit. This may affect the DTE test procedures. In some networks, the configuration of loop 3a will cause the clearing of existing connections. 3.3.3 Network Test Loop - Type 2 Loop The network test loop (test loop 2) shall be used by the telecommunications administration's test center to test the operation of leased circuits or subscriber lines and all or part of the DCE, as discussed below. Where permitted by the testing principles of the country, the DTE may use loop 2 as follows: a. In the case of a circuit-switched network, the operation of the network connection including the remote DCE shall be tested during the data transfer phase. After completion of the network loop test, it shall be possible to re-enter the data transfer phase, b. In the case of a leased circuit, the operation of the line including the remote DCE shall be tested during the idle phase. While the test is in progress, the DCE places circuits 107 and 109 in the disconnected state, circuit 104 in the binary 1 state, and circuit 142 in the connected state. The loop may be controlled manually by switches on the DCE, or automatically by the network. The control of the loop and the method used in providing automatic control shall be at the discretion of the country. In the case of leased circuit service, user control of the loop (if provided) shall be effected through circuit 104. In the event of a conflict between a call request and loop activation, the loop activation command shall have priority and the call request shall be abandoned. The exact means of testing the loop in the DCE shall be at the discretion of the country. One of the following network test loops shall be implemented. 3.3.3.1 Loop 2b
The test center of the telecommunications administration and/or the remote DTE uses this loop to test the operation of the subscriber line and all circuits of the DCE except the interchange circuit generator and the load.
When the DCE is in the loop 2b test state:
a. Connect circuit 104 to circuit 103 in the DCE; b. Connect circuit 109 to circuit 105 in the DCE c. At the interface, the DCE puts circuit 104 in the binary 1 state and circuit 109 in the disconnected state, or alternatively forms an open circuit or power disconnected state on circuits 104 and 109; d. Puts circuits 106, 107, and 125 to the DTE in the disconnected state; e. Puts circuit 142 to the DTE in the connected state f. The DCE provides timing information on circuits 114 and 115. 3.3.3.2 Loop 2a
The test center of the telecommunications administration or the remote DTE uses this loop to test the operation of the subscriber line and the entire DCE. Its configuration is the same as that given for loop 2b in clause 3.3.3.1, except for the location of the return point. 3.3.4 Subscriber line test loop - Class 4 loop 9
GB/T11599-1989
The telecommunications administration provides subscriber line test loop Class 4 (loop) for line maintenance. 3.3.4.1 Loop 4a
This loop is only provided in the case of a 4-wire subscriber line, and the telecommunications administration uses loop 4a for line maintenance. When the sending and receiving line pairs are connected together, the resulting circuit cannot be assumed to be normal. Loop 4a can be established inside the DCE or in a separate device.
When the DCE is in the loop 4a test state:
a. Circuit 104 to the DTE is set to the binary 1 state; b. Circuits 106, 107, 109 and 125 to the DTE are in the open state; c. Circuit 142 to the DTE is in the on state; d. The DCE provides timing information on circuits 114 and 115. 3.3.4.2 Loop 4b
This loop is used by telecommunications authorities to test the operation of subscriber lines including line signal conditioning circuits within the DCE. When the receive and transmit circuits are connected at this point, loop 4b provides a connection that can be considered normal. However, since the DCE does not implement complete signal regeneration, some performance may be impaired. The configuration is the same as that given for loop 4a in clause 3.3.4.1, except for the location of the return point. 3.4 Signal Symbol Timing
Whenever possible, signal symbol timing signals are transmitted to the DTE by circuits 114 and 115. In particular, signal element timing signals shall be transmitted to the DTE when operating in accordance with one of the various loops described in 3.3 above or when the DCE loses alignment or loses the input line signal. During these conditions, the tolerance of signal element timing shall be ±1%. 10
GB/T11599-1989
Appendix A
Interconnection between DTEs conforming to GB11593-89 and this standard (supplement)
It should be recognized that for DTEs that do not use half-duplex operation, interconnection between a V series DTE connected to a public data network in accordance with this standard at one end and a DTE connected to a public data network in accordance with GB11593-89 at the other end shall always be possible. Some telecommunications administrations may provide facilities to allow interconnection between DTEs conforming to GB11593-89 and DTEs conforming to this standard using half-duplex operation. This is achieved by switching circuits C, I and circuits 109, 105 according to Figure A1 during the data transfer stage. Those administrations that do not provide such facilities shall cause the DCE of GB1159389 to send r=1,=ON (connection) signal when the DTE signal circuit 105 of this standard is disconnected. For those DTEs that do not require circuit 109 to be disconnected before the signal circuit 105 is connected, half-duplex operation will be allowed.
On (-ai
UFF IRiJF)
OFF
Additional Notes:
This standard is proposed by the Ministry of Posts and Telecommunications of the People's Republic of China. Figure A1
This standard is technically coordinated by the Data Communication Technology Research Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the 30th Institute of the Ministry of Electronics. GBH
aN GHI4 Loop 3a
This loop is used to test the operation of the DTE and DCE. The loop should include the maximum number of circuits used in the operation of the DCE, including, in particular, line signal conditioning circuits. It will be recognized that in some cases it may be necessary to include various devices (e.g., attenuators, equalizers, or test loop switches) in the loop path. The subscriber line is terminated appropriately during the test state of loop 3a. The delay between the transmission and reception of test data is a number of octets (see Note). The configuration is the same as given in 3.3.2.3, except for the location of the loop return point. NOTE: In some DCEs, the configuration of loop 3a will cause a temporary loss of envelope alignment, causing a period of random signals to appear on the receiving interchange circuit. This may affect the DTE test procedures. In some networks, the configuration of loop 3a will cause the clearing of existing connections. 3.3.3 Network Test Loop - Type 2 Loop The network test loop (test loop 2) shall be used by the telecommunications administration's test center to test the operation of leased circuits or subscriber lines and all or part of the DCE, as discussed below. Where permitted by the testing principles of the country, the DTE may use loop 2 as follows: a. In the case of a circuit-switched network, the operation of the network connection including the remote DCE shall be tested during the data transfer phase. After completion of the network loop test, it shall be possible to re-enter the data transfer phase, b. In the case of a leased circuit, the operation of the line including the remote DCE shall be tested during the idle phase. While the test is in progress, the DCE places circuits 107 and 109 in the disconnected state, circuit 104 in the binary 1 state, and circuit 142 in the connected state. The loop may be controlled manually by switches on the DCE, or automatically by the network. The control of the loop and the method used in providing automatic control shall be at the discretion of the country. In the case of leased circuit service, user control of the loop (if provided) shall be effected through circuit 104. In the event of a conflict between a call request and loop activation, the loop activation command shall have priority and the call request shall be abandoned. The exact means of testing the loop in the DCE shall be at the discretion of the country. One of the following network test loops shall be implemented. 3.3.3.1 Loop 2b
The test center of the telecommunications administration and/or the remote DTE uses this loop to test the operation of the subscriber line and all circuits of the DCE except the interchange circuit generator and the load.
When the DCE is in the loop 2b test state:
a. Connect circuit 104 to circuit 103 in the DCE; b. Connect circuit 109 to circuit 105 in the DCE c. At the interface, the DCE puts circuit 104 in the binary 1 state and circuit 109 in the disconnected state, or alternatively forms an open circuit or power disconnected state on circuits 104 and 109; d. Puts circuits 106, 107, and 125 to the DTE in the disconnected state; e. Puts circuit 142 to the DTE in the connected state f. The DCE provides timing information on circuits 114 and 115. 3.3.3.2 Loop 2a
The test center of the telecommunications administration or the remote DTE uses this loop to test the operation of the subscriber line and the entire DCE. Its configuration is the same as that given for loop 2b in clause 3.3.3.1, except for the location of the return point. 3.3.4 Subscriber line test loop - Class 4 loop 9
GB/T11599-1989
The telecommunications administration provides subscriber line test loop Class 4 (loop) for line maintenance. 3.3.4.1 Loop 4abZxz.net
This loop is only provided in the case of a 4-wire subscriber line, and the telecommunications administration uses loop 4a for line maintenance. When the sending and receiving line pairs are connected together, the resulting circuit cannot be assumed to be normal. Loop 4a can be established inside the DCE or in a separate device.
When the DCE is in the loop 4a test state:
a. Circuit 104 to the DTE is set to the binary 1 state; b. Circuits 106, 107, 109 and 125 to the DTE are in the open state; c. Circuit 142 to the DTE is in the on state; d. The DCE provides timing information on circuits 114 and 115. 3.3.4.2 Loop 4b
This loop is used by telecommunications authorities to test the operation of subscriber lines including line signal conditioning circuits within the DCE. When the receive and transmit circuits are connected at this point, loop 4b provides a connection that can be considered normal. However, since the DCE does not implement complete signal regeneration, some performance may be impaired. The configuration is the same as that given for loop 4a in clause 3.3.4.1, except for the location of the return point. 3.4 Signal Symbol Timing
Whenever possible, signal symbol timing signals are transmitted to the DTE by circuits 114 and 115. In particular, signal element timing signals shall be transmitted to the DTE when operating in accordance with one of the various loops described in 3.3 above or when the DCE loses alignment or loses the input line signal. During these conditions, the tolerance of signal element timing shall be ±1%. 10
GB/T11599-1989
Appendix A
Interconnection between DTEs conforming to GB11593-89 and this standard (supplement)
It should be recognized that for DTEs that do not use half-duplex operation, interconnection between a V series DTE connected to a public data network in accordance with this standard at one end and a DTE connected to a public data network in accordance with GB11593-89 at the other end shall always be possible. Some telecommunications administrations may provide facilities to allow interconnection between DTEs conforming to GB11593-89 and DTEs conforming to this standard using half-duplex operation. This is achieved by switching circuits C, I and circuits 109, 105 according to Figure A1 during the data transfer stage. Those administrations that do not provide such facilities shall cause the DCE of GB1159389 to send r=1,=ON (connection) signal when the DTE signal circuit 105 of this standard is disconnected. For those DTEs that do not require circuit 109 to be disconnected before the signal circuit 105 is connected, half-duplex operation will be allowed.
On (-ai
UFF IRiJF)
OFF
Additional Notes:
This standard is proposed by the Ministry of Posts and Telecommunications of the People's Republic of China. Figure A1
This standard is technically coordinated by the Data Communication Technology Research Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the 30th Institute of the Ministry of Electronics. GBH
aN GHIAt the interface, the DCE places circuit 104 in the binary 1 state, places circuit 109 in the disconnected state, or alternatively forms an open circuit or power-off state on circuits 104 and 109; d. places circuits 106, 107, and 125 to the DTE in the disconnected state; e. places circuit 142 to the DTE in the connected state, f. The DCE provides timing information on circuits 114 and 115. 3.3.3.2 Loop 2a
The test center of the telecommunications administration or the remote DTE uses this loop to test the operation of the subscriber line and the entire DCE. Except for the location of the return point, its configuration is the same as that given for loop 2b in clause 3.3.3.1. 3.3.4 Subscriber Line Test Loop - Category 4 Loop 9
GB/T11599-1989
The telecommunications administration provides a subscriber line test loop Category 4 (loop) for line maintenance. 3.3.4.1 Loop 4a
This loop is provided only in the case of 4-wire subscriber lines, and the telecommunications administration uses loop 4a for line maintenance. When the transmit and receive pairs are connected together, the resulting circuit cannot be assumed to be normal. Loop 4a can be established inside the DCE or in a separate, separate device.
When the DCE is in loop 4a test state:
a. Circuit 104 to DTE is set to binary 1 state; b. Circuits 106, 107, 109 and 125 to DTE are in the disconnected state; c. Circuit 142 to DTE is in the connected state; d. DCE provides timing information on circuits 114 and 115. 3.3.4.2 Loop 4b
The telecommunications administration uses this loop to test the operation of the subscriber line including the line signal conditioning circuits within the DCE. When the receive and transmit circuits are connected at this point, loop 4b provides a connection that can be considered normal. However, since the DCE does not implement complete signal regeneration, some performance may be impaired. The configuration is the same as that given for loop 4a in clause 3.3.4.1, except for the location of the return point. 3.4 SIGNAL ELEMENT TIMING
Whenever possible, the SIGNAL ELEMENT TIMING signal is transmitted to the DTE by circuits 114 and 115. In particular, the SIGNAL ELEMENT TIMING signal is transmitted to the DTE when operating in accordance with one of the various loops described in 3.3 above or when the DCE loses alignment or loses the input line signal. During these conditions, the tolerance for SIGNAL ELEMENT TIMING should be ±1%. 10
GB/T11599—1989
Appendix A
Interconnection between DTEs conforming to GB11593-89 and this Standard (Supplement)
It should be recognized that for DTEs that do not use half-duplex operation, interconnection between a V-series DTE connected to a public data network in accordance with this Standard at one end and a DTE connected to a public data network in accordance with GB11593-89 at the other end should always be possible. Some telecommunications administrations may provide facilities to allow interconnection between DTEs conforming to GB11593-89 and DTEs conforming to this Standard using half-duplex operation. This is achieved by switching circuits C
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