This standard applies to the interconnection circuits at the interface between DTE and DCE and is called interface circuits. These circuits are used to transmit binary data, control signals and timing signals as well as appropriate analog signals. This recommendation also applies to both sides of independent intermediate equipment, which can be inserted between these two types of equipment. GB/T 3454-1982 Definition table of interface circuits between data terminal equipment (DTE) and data circuit terminating equipment (DCE) GB/T3454-1982 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
List of definitious for Interchange circuits between data terminal equipment (DTE) and data circuit-terminating equipment (DCE)1Scope
UDC 681.327
.8:621
.316.541
GB 3454-82
CCITT Recommendation V-24
1.1This standard is technically consistent with CCITT Recommendation V.24. This standard applies to the interconnection circuits at the interface between DTE and DCE and is called interface circuits. These circuits are used to transmit binary data, control signals and timing signals as well as appropriate analog signals. This recommendation also applies to both sides of independent intermediate equipment, which can be inserted between these two types of equipment (see figure). The electrical characteristics of the interface circuits are described in detail in the appropriate Recommendations on electrical characteristics or, in some special cases, in the Recommendations for the DCE.
Any type of actual equipment should be appropriately selected from the range of interface circuits specified in this Recommendation. The actual interface circuits in a particular DCE are those specified in the appropriate Recommendation. The purpose and operating requirements of the interface circuits, and the interaction between the interface circuits, are described in this Recommendation 4. The guidelines described in this Recommendation 4 are essential for the proper application of the DCE. 1.2 The DCE may include signal converters, timing generators, pulse regeneration repeaters and control circuits, as well as equipment providing other functions such as error control, automatic calling and automatic answering. Some of this equipment may be stand-alone equipment or installed in the DTE.
1.3 The range of interface circuits specified in this Recommendation may be used, for example; synchronous and asynchronous data communications
data communications on two-wire and four-wire, point-to-point or multipoint operations on leased line services! b.
Two-wire or four-wire data communication on switched network services; where short interconnection cables are used between DTE and DCE, see 2 for the description of short cables. d.
V.24 interface
Demarcation line
Intermediate equipment
[e.g.: energy control)
Description of equipment diagram
If there is no intermediate equipment, the options of A and B are the same. C is a special option for voice-activated calls. The DTE interface specified in the 1982-12-31 issued by the National Bureau of Standards
CCITT 4671
1989-1001 implementing
GB3454-82
1.4 signing wood recommendation can also be used to interconnect with public data networks. For these cases, additional information on the implementation and operating requirements of the interface circuit is recorded in the X series customer recommendations. 2 Demarcation line
The interface between DTE and DCE is located at the connector, which is the interface point between these two types of equipment. For interface circuits related to signal conversion or similar equipment, and for interface circuits related to automatic calling equipment (ACE), separate connectors can be provided. For the mechanical characteristics of the interface, see ISO2110［11 or ISO4902［2. The connector does not have to be actually installed on the DCE, but can be installed in a fixed position near the DTE. DTF usually provides one interconnecting cable or multiple cables. It is recommended to use short cables. The length of the cable is limited only by the load capacitance and other electrical characteristics specified in the relevant electrical characteristics recommendations. 3 Definition of interconnection circuits
3.1100 series--share application
The names of these interface circuits are listed in table 1 in tabular form. Table 1100 series interface circuit list
Circuit name
Postcard ground or common return
DTE common return
DCE common return
Common write line
Send data
Receive data
Request to send
Ready to send
Data equipment ready
Connect data equipment to line
Data terminal ready
Data channel receive line signal detector
Data signal Quality detector
Data signal rate selector (DTE)
Data signal rate selector (DCE)
Transmitter signal symbol timing (DTE)
Transmitter estimate symbol timing (DCE)
Receiver signal symbol timing (DCE)
Select backup equipment
Each equipment indicator
And send data to the channel
Return channel receive data
Send reverse channel line signal
Reverse channel standard Ready
Lu name
Reverse co-channel receive line signal detector
Reverse channel signal quality detector
Select frequency group
Call indicator
Select transmit frequency
Select receive frequency
Receiver signal symbol timing (DTE)
Request receive
Send reverse question tone
Receive character timing
Return to non-data mode
Receive ready
Receive data present| |tt||New signal
Loopback/maintenance test
Local bad return
Full test indicator
Sent voice answer
Received voice answer
GB3454-82
Continued Table 1
Circuit 102 - Signal ground or common return
This conductor conforms to the electrical characteristics of Recommendation V.28 to establish a signal common return for unbalanced interface circuits and conforms to Recommendations V.10, V.11 and V.35 to establish a current reference potential for interface circuits. Within the DCE, this circuit shall be connected to a point that can be connected to the protective earth or ground by a metal strap within the equipment. This metal strap may be connected or removed during installation, depending on applicable safety regulations or the requirement to minimize the introduction of noise into electronic circuits. Care should be taken to avoid the establishment of ground loops that carry large currents. Circuit 102a-
DTE common through line
This conductor is connected to the common return line of the DTF circuit and is used as the reference potential of the unbalanced interface circuit receiver recommended by V.10 in CE.
DCE common return line
Circuit 102b-
This conductor is connected to the common return line of the DCE circuit and is used as the reference potential of the unbalanced interface circuit receiver recommended by V.10 in DTE.
Note: In the case of mixing V.10U and V.11 recommended circuits in the indirect gate, it is necessary to formulate separate cases for the common return line of V.10 recommended circuits 12a and 102b and the wiring of the true current reference potential conductor or the wiring of the protective ground wire. Circuit 102G-Common return line
In some cases where the common return line is used, according to V.31 recommended electrical characteristics, this conductor is a single-stream interface circuit controlled by contact closure, establishing a common signal return line.
In equipment with interface circuit signal sources, this conductor, whether located in DCE or DTE, must be isolated from the signal ground or protection ground.
Circuit 103 - Send data
Side: To DCE
GB 854--82
Data signals initiated by DTE and sent to one or more remote data stations through the data channel, or data signals sent through DCE for maintenance test purposes under the control of DTE, must be sent to DCE on this circuit. Circuit 104 -
- Receive data
Direction: From DCE
Data signals generated by DCE in response to data channel line signals sent by remote data stations, or data signals generated in response to DTE maintenance test signals, are sent to DTE via this circuit. Note: The receiving status of the maintenance test signal shall be in accordance with the provisions of electrical schematic I core 7. Circuit 105 - Request to Send
Direction: To DCE
The signal on this circuit controls the sending function of the DCE data channel. The "on" state enables the DCE to adopt the sending mode of the data channel. The "off" state, when all the data transmitted on circuit 103 has been sent, the "off" state enables the DCE to adopt the non-sending mode of the data channel.
Circuit 106 - Ready to Send
Direction: From DCE
The signal on this circuit indicates whether the DCE is ready to receive data signals sent on the data channel, or data signals used for maintenance test purposes under the control of DTE.
The "on" state indicates that the DCE is ready to receive data signals from the DTE. The "off" state indicates that the DCE is not ready to receive data signals from the DTE. Receive data signals from DTE. Circuit 107 - Data Equipment (Data Transmitter) Ready Direction: From DCE
The signal on this circuit indicates whether the DCE is ready to work. "On" state: When circuit 142 is in the "off" state or circuit 142 is not installed, the "on" state indicates that a signal converter or similar equipment has been connected to the line, and the DCE is ready to further exchange control signals with the DTE to start data transmission.
*The "on" state together with the "on" state of circuit 142 indicates that the DCE is ready to exchange data signals with the DTE for maintenance test purposes.
The "off" state indicates that the DCE is not ready to work. Circuit 108/1 - Connect a data device (data transmitter) to the line Direction: To DCE
The signal on this circuit is to control the switching of the signal conversion equipment or similar equipment to the line or disconnect the line. The "on" state causes the DCE to connect the signal conversion equipment or similar equipment to the line. "Off" state, when all data previously transmitted to the line through circuit 103 and/or circuit 118 have been transmitted, the "off" state causes the DCE to disconnect the signal conversion equipment or similar equipment from the line. Circuit 108/2 - Data Terminal Ready
Between: To DCE
The signal on this circuit is the switching that controls the signal conversion equipment or similar equipment to be connected to or disconnected from the line. "On" state, indicates that the DTE is ready to work. This state causes the DCE to prepare to connect the signal conversion equipment or similar equipment to the line, and to maintain this connection after the connection is established using auxiliary means. And when the DTE is ready to send or receive data, the DTE is allowed to assume the "on" state on circuit 108/2. "Off" state: when all data previously transmitted through circuit 103 and/or circuit 118 have been transmitted, the "off" state causes the DCE to disconnect the signal conversion equipment or similar equipment from the line. Circuit 109 -
Data channel receive line signal detector
Direction: from DCE
GB 3454--82
The signal on this circuit indicates whether the line signal on the received data channel is within the appropriate limit range, as specified in the relevant DCE recommendations.
The "on" state indicates that the received signal is within the appropriate limit range. The "off" state indicates that the received signal is not within the appropriate limit range. Circuit 110 - Data signal quality detector
Direction: from DCE
The signal on this circuit indicates whether there is a reasonable probability of an error in the data received on the data channel, and the signal quality shown is in accordance with the provisions of the relevant DCF recommendations.
The "on" state indicates that there is no reason to believe that an error has occurred. The "off" state indicates that there is a reasonable probability of error. Circuit 111 - A Data Signal Rate Selector (Source DTE) Direction: To DCE
The signal on this circuit is used to select a rate from one of the two data signal rates of a dual-rate synchronous DCE, or from a dual-rate range.The "ON" state selects the higher rate or rate range. The "OFF" state selects the lower rate or rate range. Circuit 112—
—Data Signal Rate Selector (Source FDCE) Direction: From DCE
The signal on this circuit is used to select one of the two data signal rates or rate ranges within the DTE to match the data signal rate rate range used by the dual-speed synchronous DCE or the dual-speed asynchronous DCF. The "ON" state selects the higher rate or rate range. The "OFF" state selects the lower rate or rate range. Circuit 113—Transmitter Signal Symbol Timing (Source DTE) Direction: To DCE
The signal on this circuit provides signal symbol timing information to the DCE. The state passband on this circuit should be "ON" and "OFF" states of equal cycle time. The transition from "ON" to "OFF" state should usually be in the middle of each signal symbol on circuit 103. Circuit 114 - Transmitter Signal Symbol Timing (from DCE) Direction: From DCE
The signals on this circuit provide the DTE with signal symbol timing information. The states on this circuit should normally be "on" and "off" states with equal cycle times. The DTE should send a data signal to circuit 103, and the transition between signal symbols usually occurs when circuit 114 changes from "off" to "on". Circuit 115 Receiver Signal Symbol Timing (from DCE) Direction: From DCE
The signals on this circuit provide the DTE with signal symbol timing information. The states on this circuit should normally be "on" and "off" states with equal cycle times, and the transition from "on" to "off" state will usually be in the middle of each signal symbol on circuit 104. Circuit 116 Select Spare Equipment
Direction: To DCF
The signals on this circuit are used to select active or spare equipment, such as signal converters and data channels. The "ON" state selects the alternate mode of operation, causing the DCE to replace the intended equipment with its alternate equipment. The "OFF" state causes the DCE to replace the alternate equipment with normal equipment. Once the use of the alternate equipment is not required, this circuit will remain in the "OFF" state.
Circuit 117—Alternate Equipment Indicator
GB 3454—82
Direction: From DCE
The signal on this circuit indicates whether the DCE has been adjusted to operate in its alternate mode and has replaced the intended equipment with its alternate equipment.
The "ON" state indicates that the DCE has been adjusted to operate in its alternate mode. The "OFF" state indicates that the DCE has been adjusted to operate in its normal mode. Circuit 118—Reverse Channel Send Data
Direction: To DCE
This circuit is equivalent to circuit 103. It is only used to send data over the reverse channel. Circuit 119 - Reverse Channel Receive Data
Direction: From DCE
This circuit is equivalent to circuit 104, but it is used to receive data over the reverse channel. Circuit 120 - Transmit Reverse Channel Line Signal Direction: To DCE
This circuit is equivalent to circuit 105, but it is used to control the DCE reverse channel transmit function. The "on" state puts the DCE in reverse channel transmit mode. The "off" state, when all data transmitted on circuit 118 has been sent to the line, the "off" state puts the DCE in reverse channel non-transmit mode.
- Reverse Channel Ready
Circuit 121 -
Direction: From DCE
This circuit is equivalent to circuit 106, but it is used to indicate whether the DCE has been adjusted to send data on the reverse channel. The "on" state indicates that the DCE has been adjusted to send data on the reverse channel. The "off" state indicates that the DCE has not been adjusted to send data on the reverse channel. Circuit 122 - Reverse Channel Received Line Signal Detector Direction: From DCE
This circuit is equivalent to circuit 109, but it is used to indicate whether the received reverse channel line signal is within the appropriate limits specified in the relevant DCE recommendations.
Circuit 123 - Reverse Channel Signal Quality Detector Direction: From DCE
This circuit is equivalent to circuit 110, but it is used to indicate the signal quality of the received reverse channel line signal. Circuit 124 Select Frequency Group
Direction: To DCE
The signal on this circuit is used to select the required frequency group from the frequency groups available to the DCE. The "on" state causes the DCE to use all frequency groups to represent the data signal. The "off" state causes the DCE to represent the data signal according to the specified compressed number of frequency groups. Circuit 125
- Call Indicator
Direction: From DCE
The signal on this circuit indicates whether the DCE is receiving a call signal. The "on" state indicates that a call signal is being received. The "off" state indicates that no call signal is received, and this state can also occur when the pulse modulated call signal is interrupted. Circuit 126 - Select transmit frequency
Direction: To DCE
The signal on this circuit is used to select the transmit frequency required by the DCE. The "on" state selects a higher transmit frequency. The "off" state selects a lower transmit frequency. Circuit 127 - Select receive frequency
GB3454--82
Direction: To DCE
The signal on this circuit is used to select the receive frequency required by the DCE. The "on" state selects a lower receive frequency. The "off" state selects a higher receive frequency. Circuit 128 - Receiver signal symbol timing (from DTE) Direction: To DCE
The signal on this circuit provides signal symbol timing information to the DCE. The cycle time of the state on this circuit should normally be equal between the "on" and "off" states. The DCE should present a data signal on circuit 104, and the transition between its signal code elements should normally occur when the signal on circuit 128 transitions from the "off" state to the "on" state. Circuit 129 - Request to receive
Direction: to DCE
The signal on this circuit is used to control the receiving function of the DCE. The "on" state puts the DCE in receiving mode. The "off" state puts the DCE in non-receiving mode. Circuit 130 - Send reverse channel tone
Direction: to DCE
The signal on this circuit controls the sending of reverse channel tone. *The "on" state causes the DCE to send a reverse channel tone. The "off" state causes the DCE to stop sending a reverse channel tone. Received character timing
circuit 131 -
direction: incoming DCE
The signal on this circuit provides the DTE with information about the character timing specified by the DCE recommendations. Circuit 132 - Return to non-data mode
direction, to DCE
The signal on this circuit is used to restore the non-data mode provided by the DCE without releasing the line connection with the remote station. The "on" state causes the DCE to restore the non-data mode. After the non-data mode is established, this The circuit must be changed to the "off" state. Circuit 133 - Receive Ready
Direction: To DCE
The signal on this circuit controls the data transmission on circuit 104, indicating whether the DTE is able to accept a given amount of data (such as a group of data), the amount of data being specified in the recommendations of appropriate intermediate equipment such as error control equipment. "On" state; whenever the DTE is able to accept data, the "on" state must be maintained and the intermediate equipment sends the received data to the DTE.
*The "off" state indicates that the DTE cannot accept data and causes the intermediate equipment to retain the data. Circuit 134 -
Data Present
Direction: From DCE
The signal on this circuit is used to separate the information message transmitted by circuit 104 from the supervisory information, as specified in the recommendations of appropriate intermediate equipment such as error control equipment.
The "on" state indicates that the data is data of the information message. "Off" state: The "off" state should be maintained at all other times. Circuit 136 New Signal
Direction: To DCE
The signal on this circuit is used to control the response time of the DCE receiver. GB3454—82
"On" state: The "On" state of circuit 136 commands the DCE receiver to prepare itself for rapid detection of the disappearance of the signal. (For example, stop the response time circuit associated with circuit 109). After the received line signal drops below the threshold of the receive line signal detector, the DCE will, a., turn circuit 109 to the "Off" state; h., the receiver is ready to quickly detect the presence of a new line signal (for example, reset the receiver timing recovery circuit). Once circuit 136 is turned "On", circuit 136 can be turned "Off" after a code element interval and must be turned "Off" after circuit 109 is turned "Off". At all other times, circuit 136 should be in the "Off" state.
Local Loopback/Maintenance Test
Circuit 140
Direction, to DCE
The signals on this circuit are used to start and release the state of the loop or other maintenance test in the DCE. The "On" state enables the maintenance test state. The "Tear" state releases the maintenance test state. Circuit 141-
Local Loopback
Direction: to DCE
The signals on this circuit are used to control the test state of loop 3 in the local DCE: "On" state: The "On" state of circuit 141 is the test state of establishing loop 3 in the local DCE. "Disconnected" state: The "disconnected" state of circuit 141 is the test state of releasing the bad circuit 3 in the local DCE. Circuit 142 - Test indicator
Direction: from DCE
The signal on this circuit indicates whether it is in maintenance state. The "connected" state indicates that the DCE is in maintenance state and cannot receive data signals from the remote DTE or send data signals to the remote DTE.
The "disconnected" state indicates that the DCE is not in maintenance test state. Circuit 191 - Send voice answer
Direction: to DCE| |tt||The signal generated by the voice answering unit in the DTE is sent to the DCE through this circuit. The electrical characteristics of this analog interface circuit are part of the corresponding DCE recommendations.
Circuit 192---Receive Voice Answering
Direction: The voice signal generated by the voice answering unit of the remote DTF from the DCE is received by the DCE and sent to the DTE through this circuit. The electrical characteristics of this analog interface circuit are part of the corresponding DCE recommendations. 3.2200 Series - Dedicated to Automatic Calling
These interface circuits are shown in Table The format is listed in Table 2. For the process of automatic calling, see Recommendation V.25 for the public switched network and Recommendation S16 for the user1 telegraph network [3]. Table 2 20 series interface circuits dedicated to automatic calling Interface circuit number
Interface circuit name
Signal ground or public return line
Call request
Data line busy
Remote station connected
Abandon call
Digital signal (2″)
From DCF
To DCE
Interface circuit number | |tt||Circuit 201-
GB8454-82
Continued Table 2
Interface circuit name
Digital signal (21)
Digital signal (22)
Digital signal (2\)
Present a digit
Digital present
Power indication
-Signal ground or common return
From DCE
To DCE
This conductor is used to establish a common reference potential for signals for all 200 series interface circuits. In the automatic calling equipment, this circuit must be connected to a point, and it should be possible to connect this point to the protective earth or earth in the equipment by a metal strap. This metal strap may be installed or removed during installation according to applicable safety regulations or in accordance with the requirements to minimize the introduction of noise into the electronic circuit. Care should be taken to avoid the establishment of a ground loop carrying large currents. Circuit 202 - Call Request
Direction: To DCE wwW.bzxz.Net
The signal on this circuit is used to put the automatic call equipment in a state where it can make a call, and to connect the automatic call equipment to the line, or to disconnect the automatic call equipment from the line.
The "On" state enables the DCE to put the automatic call equipment in a state where it can make a call and connect the equipment to the line. The "Off" state disconnects the automatic call equipment from the line and indicates that the DTE has released the automatic call equipment. - Data Line Busy
Circuit 203 -
Direction: From DCE
The signal on this circuit indicates whether the relevant line is in use (for example, for automatic call data transmission or voice communication, test process). The "On" state indicates that the line is in use. The "Off" state indicates that the line is not in use, so the DTE can make a call. Circuit 204 - Remote Station Connected
Direction: From DCE
The signal on this circuit indicates whether a connection has been established with a remote data station (or telegraph station). The "connected" state indicates that a signal has been received from the remote DCE signaling device, indicating that a connection has been established with the device. "Disconnected" state: The "disconnected" state should be maintained at all other times. Circuit 205 - Call Awaited
Direction: From DCE
The signal on this circuit indicates whether a predetermined time has passed between successive events during a call. The "connected" state indicates that the call should be abandoned. The "disconnected" state indicates that the call can continue. Digital signal circuits:
Circuit 206 - Digital signal (2\)
Circuit 207 - Digital signal (2\)
Circuit 208 Digital signal (22)
Circuit 209 - Digital signal (23)
Direction: To DCE
DTE provides the coding combinations shown in Table 3 on these circuits; these coding combinations are the digital number of the called data station (or user telegraph station) and the control characters that demarcate the boundaries.
Control character EON
Control character SEP
GB8454-82
Number status
The control character FON (end of number) causes the DCE to take appropriate action and wait for the response from the called data station. The control character SEP (separation) indicates that a pause is required between consecutive digits or before a string of digits, and SEP also causes the automatic calling equipment to insert an appropriate time interval. The coding combinations listed in the table above are intended for use with equipment using the V.25 and S.16 recommendations. Circuit 210 - Present Next Digit
Direction: From DCE
The signal on this circuit indicates whether the automatic calling equipment is ready to receive the next coding combination. The "ON" state indicates that the automatic calling equipment is ready to receive the next coding combination. The "OFF" state indicates that the automatic calling equipment is also ready to receive signals on the digital signal circuit. Circuit 211 -
Digital Present
Direction: To DCE
The signal on this circuit controls the reading of the coding combination presented on the digital signal circuit. The "ON" state enables the automatic calling equipment to read the coding combination presented on the digital signal circuit. The "OFF" state: The "OFF" state on this circuit prevents the automatic calling equipment from reading the coding combination on the digital signal circuit. Power indication
Circuit 213-
Direction, from DCE
The signal on this circuit indicates whether there is power in the automatic calling equipment. The "on" state indicates that there is power in the automatic calling equipment. The "off" state indicates that there is no power in the automatic calling equipment. 3.3 Circuit Fault (Electrical)
Where the following interface circuits are installed, these circuits should be used to detect the equipment connected through the interface, detect its power-off state or the disconnection state of the interconnecting cable:
Circuit 105-Request to send
Circuit 107-Data equipment ready
Circuit 108/1-Connect data equipment to line 108/2-Data terminal ready
Circuit 120-Send reverse channel line signal Circuit 202-
Call request
Circuit 213-Power indication
GB 3464-82
In the recommendations on electrical characteristics, a standard for determining a fault state should be specified. The receiver of these circuits should regard the power-off state or the disconnection of the interconnecting cable as the "disconnected" state on these circuits. 3.4 Termination of connection circuits
According to the definition of the new interface circuits and the table of non-essential (i.e. optional) circuits in addition to the basic circuits in the V series recommendations for DCE, the receiver circuits may be provided in the DTE or DCE with the generator in the auxiliary equipment. Therefore, in the equipment in which the receiver is installed, means should be provided to inhibit or ignore any possible false start of the receiver when the receiver is not connected to the generator. Operation requirements
The following are the operating requirements for using the connection 1.1 circuits and explain in detail the required relationship between them when the interface circuits are installed. 4.1 Data circuits
It is obvious that when the required state is not present on the installed interface control circuit, normal data transmission may be impaired. Therefore, the DTE should not transmit data on circuit 103 unless the "on" state is present on all four of the following circuits (if these circuits are provided), namely 105, 106, 107, 108/1 or 108/2. When the above four circuits are all in the "on" state, all data transmitted on circuit 103 shall be sent by DCE. For more details, see 4.4 and 4.5.
Unless the following four circuits are all in the "on* state, the DTE shall not transmit data on circuit 118.
When the above four circuits are all in the "on" state, all data transmitted on circuit 118 shall be sent by DCE. 4.2 Idle Periods
During the intervals when circuits 105 and 106 are in the "on" state and there is no data to be sent, the DTE may send a "binary 1" state, or send multiple inversions or other sequences such as the SYN code character to maintain timing synchronization, or send idle characters used in accordance with the data link control procedure, etc.
Where special requirements are used, they are explained in the relevant DCE recommendations. 4.8 Clamping
4.3.1 In all applications, if the following voltages are provided, the DCE shall maintain: a. When circuit 109 is in the "off" state, the DCE shall maintain circuit 104 in the binary "1" state. b. When circuit 122 is in the "off" state, the DCE shall maintain circuit 119 in the binary "1" state. 4.3.2 In addition, when the DCE is forced to operate in half-duplex on a two-wire line, the DCE shall maintain: 9. When circuit 105 is in the "on" state, the DCE shall maintain circuit 104 in the binary "1" state and circuit 109 in the "off" state. Furthermore, after a transition from "on" to "off" occurs on circuit 105, the states of the above two circuits should be maintained for a short time (this is specified in the relevant DCE recommendations). b When circuit 120 is in the "on" state, the DCE should maintain circuit 119 in the binary "1" state and maintain circuit 12 in the "off" state, and after a transition from "on" to "off" occurs on circuit 120, the states of the above two circuits should be maintained for a short time (this is specified in the relevant DCE recommendations). 4.4 Operation of circuits 107, 108/1 and 108/2 The signal on circuit 107 should be regarded as a response to the start line connection signal (such as circuit 108/1), however, it is not possible to expect adjustments to the data channel, such as equalization and de-clamping, before circuit 107 changes to the "on" state. When circuit 108/1 or 108/2 is changed to the "off" state, and the DCE has not changed circuit 107 to the "off" state, circuit 108/1 or 108/2 should not be changed to the "on" state again. A jumper selection should be provided in the DCE to select the operation of circuit 108/1 or circuit 108/2. When the DCE is adjusted to automatically answer calls, it can only connect to the line when it responds to both the call signal and the "on" state on circuit 108/2.
In some occasions where leased circuits are used, circuit 108 may not be provided. In this case, the state on this circuit can be regarded as permanently in the "on" state.
GB 3454-82
Under certain test conditions, both DTE and DCE can use certain interface circuits. It should be understood that when circuit 107 is in the "off" state, DTE will ignore the states given from the DCE interface circuit except those on circuit 125 and the timing circuit. In addition, when circuit 108/1 or 108/2 is in the "off" state, DCE will ignore the states given from the DTE interface circuit. Therefore, the "on" state on circuits 107 and 108/1 or 108/2 is a prerequisite for receiving the signals given by the DCE or DTE interface circuit (except circuit 125) as valid signals. The "off" state on circuits 108/1 or 108/2 should not interrupt the operation of circuit 125. Under the loop test conditions specified in the V.54 recommendation, when D When the DTE is not participating in maintenance testing, circuit 107 should be in the "off" state and should not respond to circuits 108/1 and 108/2. When the DTE participates in maintenance testing with a local or remote DCE, circuit 142 should be in the "on" state and circuit 107 should respond to circuits 108/1 or 108/2. 4.5 Relationship between circuits 103, 105 and 106 The DTE indicates that it wants to send data by turning circuit 105 to the "on" state. Then, the DCE's task is to enter the sending mode, that is, to prepare to send data, and also to remind the remote DCE to adjust itself to a state where it can receive data. The DCE enters the sending mode and reminds the remote DCE to adjust itself to a state where it can receive data. The method used to adjust the remote DCE is described in the corresponding DCE recommendation. When the transmitting DCE changes circuit 106 to the "on" state, the DTE is allowed to send data through the interface of circuit 103. Changing circuit 106 to "on" means that all data will be transmitted to the line through the interface until any of the four circuits 105, 106, 107, 108/1 or 108/2 is changed to the "off" state again. However, the "on" state of circuit 106 does not necessarily guarantee that the remote DCE is in receive mode (there may be a delay between the time it takes to transmit a bit through the interface and the time it takes for the signal code element representing this bit to be sent to the line). , which ranges from less than 1 millisecond to several seconds. The amount of delay depends on the complexity and sophistication of the signal converters sending the signals).
DT should not change circuit 105 to the "break:open" state before the last bit (data bit or stop unit) has been transmitted through the interface LI of circuit 103. Similarly, in certain full-duplex switching network applications where circuit 105 is not provided (see special DCE recommendations), this requirement also applies when circuit 108/1 or 108/2 is changed to the "break" state to terminate a call in the secondary switching network. Where circuit 105 is provided, the "make" and "break" states on circuit 106 should be responsive to the "make" and "break" states of circuit 105. For the appropriate response time of circuit 106, and the operation of circuit 106 when circuit 105 is not provided, see the relevant DCE construction.
When both circuit 105 and circuit 106 are in the "break" state, the DTE should maintain the binary "1" state on circuit 103. When circuit 105 is changed to the "off" state, the DCE shall not change circuit 105 to the "on" state again before circuit 106 is changed to the "off" state.
NOTE: These conditions also apply to the relationship between circuits 120, 121 and 118. 4.6 Timing Circuits
Timing information transmitted through the interface should preferably not be limited to the period during which data is actually being transmitted. However, during the time interval when no timing information is transmitted through the interface, the relevant circuit should remain in the "off" state. The following conditions apply: 4.6.1 Circuit 113 - Transmitter signal code element timing source DTE) Where circuit 113 is used, the DTE shall continuously transmit timing information on this circuit through the interface when the DTE is in the power-on condition and the timing source in the DTE is capable of generating timing information. 4.6.2 Circuit 114 - Transmitter Signal Symbol Timing (from DCE) Where circuit 114 is used, the DCE shall continuously transmit timing information on this circuit through the interface when the DCE is in the power-on condition and the timing in the DCE can generate timing information for the entire time. However, it should be noted that the DCE, which obtains power from the battery in the central office through the local telephone loop, is in the power-off state when the loop is disconnected (i.e., when the handset is on-hook). 4.6.3 Circuit 115 - Receiver Signal Symbol Timing (from DCE) Where circuit 115 is used, the DCE shall continuously transmit timing information over this circuit through the interface for all the time that the timing source is capable of generating such information.
It should be recognized that when the DCE is disconnected from the line, the DCE, which receives power from the central office through the local loop, is disconnected from the power supply and the timing source ceases to operate. It should also be recognized that some timing sources will not continue to operate indefinitely if there is no driving (external synchronization) signal.
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