This standard applies to user telegraph and low-speed data communication networks, using frequency modulation to open 50 bit/second data. This standard specifies the tolerance of various damage factors in the transmission path to ensure the quality of data transmission of 50 bit/second transmission. This standard is the basis for the design of transmission data communication systems and the formulation of maintenance standards. GB/T 4827-1984 50 bit/second data transmission requirements GB/T4827-1984 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
GB/T4827—1984
Requirements of data transmission at 50 bit/s1984-12-26Promulgated
National Bureau of Standards
Implementation on 1985-10-01
National Standard of the People's Republic of China
Requirements of data transmission at 50 bit/sUDC621.391
.6：621.394
GB/T4827—1984
This standard applies to user telegraph and low-speed data communication networks, using frequency modulation telegraph channels to open 50 bit/s data. This standard specifies the tolerance of various damage factors in the transmission path to ensure the quality of data transmission of 50 bit/s telegraph channels. This standard is the basis for the design of telegraph channel data communication systems and the formulation of maintenance standards. 1 Transmission quality
1.1 The composition of the data transmission link is shown in Figure 1. City Broadcasting Circuit
Ya Tun Institute
: Zhonglu
Yiji Department
Figure 1 Composition of the data transmission link
From the output point (point A) of the data terminal equipment* to the input point (point A) of the opposite data terminal equipment, including the sending and receiving user circuits, relay circuits (N sections) and data switches (N+1) constitute the entire 50 bit/s data signal transmission link. The user circuit can adopt DC transmission mode, AC transmission mode or a combination of these two modes. DC transmission mode is further divided into single-stream transmission, dual-stream transmission and tri-state current transmission. AC transmission mode can be realized by frequency modulation transmission circuit opened by solid line or carrier voice circuit. Other transmission modes can also be realized by solid line. As shown in Figure 2. The composition of the relay circuit is shown in Figure 3. *Data terminal equipment includes a computer with a communication controller that can send and receive data. Issued by the National Bureau of Standards on December 26, 1984, and implemented on October 1, 1985. GB/T4827-1984. Figure 2: User circuit. Receive notification and Chinese translation. "Travel, GB/T4827-1984. Ten output control. Relay circuit. The carrier audio path is a circuit between a pair of transmitters, including the carrier voice path and the voice relay lines at both ends. 1.2 Interface parameters. 1.2.1 Interface parameters between FM transmitter and real line circuit: a. The total power sent by the FM transmitter to the real line circuit shall not exceed 1mw ( odBm). The corresponding single reporting channel transmission power limit is as specified in Table 1.
Number of reporting channels opened by FM broadcasting machine
12 channels or less
13 to 18 channels
19 to 24 channels
Transmission frequency band 300~3400Hz
Impedance 600Q (balanced)
Average transmission power (level) of single reporting channel
83.3μwo(-10.8dBm0)
55.6μw0(12.6dBm0)
41.7μW0(-13.8dBm0)
1.2.2 The interface parameters between FM broadcasting machine and carrier voice channel comply with the relevant provisions of GB3384-82 "Network Interface Parameters of Analog Carrier Communication System":|| tt||Transmission frequency band 300~3400Hz
Impedance 6002 (balanced)
Transmit power
At the zero relative level point, the total transmit power shall not exceed 135μWO or 50μW0*When the total transmit power limits are 135μWO and 50μWO respectively, the average transmit power limits of a single reporting channel shall be as specified in Table 2. *When the total average transmit power of 50μWO (-13dBm0) is adopted, other requirements for the audio channel are shown in Appendix A. 3
Number of reporting channels opened by FM radio
12 channels or less
13 to 18 channels
19 to 24 channels
GB/T4827—1984
Average transmit power of a single reporting channel
1 35μw0(—8.7dBm0)
11.25μw0(-19.5dBm0)
7.5μW0(-21.3dBm0)
5.6μW0(—22.5dBm0)
50μW0(-13dBm0)
4.17μW0(-23.8dBm0)
2.78μW0(-25.6dBm0)
2.08μW0(26.8dBm0)
When reporting data and other services are transmitted simultaneously on the same carrier line, the total average transmission power for one minute shall not exceed 50μW0 (—13dBm0), of which the total power allocated to data signals shall not exceed 10μW0 (—20dBm0). 1.3 Bit error rate and signal distortion
1.3.1 Bit error rate
The bit error rate does not exceed 4×10-6
The probability of meeting the above indicators is above 95%. 1.3.2 Distortion tolerance of the reporting data transmission link 1.3.2.1 The starting and ending distortion of the DC loop end point [point c in Figure 2 (a) and point B in Figure 2 (b) and ()] in the sending user circuit does not exceed 10%.
1.3.2.2 The distortion tolerance of the AC transmission part of the user circuit [BC section and B'C section in Figure 2 (b) and (c)] is the same as that of the relay circuit. See Table 3.
1.3.2.3 The distortion of the switch (or user concentrator) does not exceed 2%. 1.3.2.4 The receiving correction power of the switch with signal regeneration performance is not less than 40%, and the sending distortion does not exceed 3%. The distortion tolerance of the relay circuit is shown in Table 3.
Reporting route transfer
Number of connections
Using 1:1 signal to measure
Equi-temporal distortion (%)
Measured with pseudo-random sequence
Isochronous distortion (%)*
Measured with pseudo-random sequence
Intrinsic start-end distortion"
Note: The tolerance specified in Table 3 applies to circuits between switches with signal regeneration function, and also to circuits from the terminal to the regeneration switch closest to the terminal.
Transmission path impairment factor tolerance
2.1 User circuit
2.1.1 DC loop transmission tolerance
2. 1.1.1 The insulation resistance between core wires and between core wires and ground measured by a 250V megohmmeter should be no less than 20M2. 2.1.1.2 The core wire loop resistance shall not exceed 2k9, and the unbalanced resistance shall not exceed 1% of the loop resistance. 2.1.1.3 For user circuits with the earth as the loop, the grounding resistance of the telegraph office's single-line working loop shall comply with the provisions of Table 4. The grounding resistance at the user end shall not exceed 202.
*Pseudo-random sequences include 511 codes, SQ9, SQK and domestic test telegrams. Isochronous distortion can also be measured using 1:6 and 6:1 isochronous signals. 4
Number of incoming lines
Working grounding resistance (Q)
2.1.2 Solid line audio pass 2.1.2.1 Net attenuation
GB/T4827—1984
Below 10
Taking 3200Hz as the measurement signal frequency, the net attenuation shall not exceed 26dB. 2.1.2.2 Random noise
Above 51
Measured at the audio receiving line point of FM audio telegraph equipment (or similar equipment, such as modem), the weighted random noise level shall be 37dB lower than the receiving level of the measurement signal (the transmission level is 0dBm, the same below). 2.1.2.3 Impulse noise
Measured at the audio receiving line point of FM audio telegraph equipment (or similar equipment, such as modem) When measured at the receiving point, the pulse count exceeding the threshold level of 9dB lower than the measured signal receiving level shall not exceed 18 times within 15 minutes. 2.1.2.4 Single-frequency interference
When measured at the audio receiving point of FM audio telegraph equipment (or similar equipment, such as a modem), the interference level of any single frequency in the range of 300 to 3400Hz shall be 49dB lower than the measured signal receiving level. 2.1.3 Tolerance of carrier audio channel transmission impairment factor The tolerance of carrier audio channel impairment factor in user circuits is the same as that specified in Article 2.2. 2.2 Relay circuit
The tolerance of carrier audio channel transmission impairment factor used for relay circuits is as follows: 2.2.1800Hz net attenuation
The nominal value is 0dB. Among them, the net attenuation of the disconnected line in the transmitting and receiving telegraph, including the attenuator and the equalizing and amplifying equipment installed when necessary, is 14dB. The net attenuation of the receiving telegraph trunk is 4dB. 2.2.2 Net attenuation variation over time
The difference between the average value of the net attenuation and the nominal value shall not exceed 0.5dB. The standard deviation of the average value shall not exceed 1.5dB. 2.2.3 Random noise
The weighted noise shall not exceed -45dBmOp.
The crosstalk level of the transmitting and receiving telegraph trunks shall not exceed -61dBmOp respectively. 2.2.4 Impulse noise
Within 15min, the pulse count exceeding the threshold level of -18dBm0 shall not exceed 18 times. 2.2.5 Frequency deviation
The frequency deviation shall not exceed 2Hz (positive or negative).
2.2.6 Attenuation frequency characteristics
The attenuation frequency characteristics of the carrier voice circuit shall comply with the provisions of Table 5. The difference between the attenuation in the range of 300 to 3400 Hz and the net attenuation at 800 Hz for the transmitting and receiving voice trunks shall not exceed 2.6 dB. 5
Single frequency interference
Frequency range (Hz)
Below 300
300~400
400~600
600~3000
3000~3200
3200~3400
Above 3400
4827—1984
Net attenuation relative to 800Hz (dB)
Not less than -2.2, upper limit not specified
—2.2~2.2
—2.2~3.0
—2.2~7. 0
Not less than -2.2, upper limit not specified
In the frequency band of 300～3400Hz, the interference level of any single frequency shall not exceed -68dBm0. 2.2.8
Power supply interference
When a sinusoidal signal of 0dBm0 passes through the audio path, its maximum sideband component shall not exceed -45dBm0. 2.2.9Crosstalk protection
The crosstalk protection between the transmitting and receiving circuits of the same carrier voice channel shall not be less than 43dB. The inter-channel crosstalk protection of the carrier voice channel shall not be less than 58dB. With the upper limit, in addition to the net attenuation and attenuation frequency characteristics already specified, other tolerances also apply to the carrier voice channel. 6
GB/T4827—1984
Appendix A
When the total average power of the reporting data transmission signal is 50uWO, the attenuation frequency characteristics of the audio path and the tolerance of impulse noise (supplement)
The attenuation frequency characteristics should not exceed the limit values ​​in the following table Frequency range (Hz)
Below 300
300~500
500~2800
2800~3000
3000~32 50
3250~3350
Above 3350
Net attenuation relative to 800Hz (dB)
Not less than -2.0, upper limit not specified
—2.0~3.0
—2.0~4.0
—2.0~7.0
Not less than -2.0, upper limit not specified
A.2 Within 15 minutes, the pulse count exceeding the threshold value of -28dBm0 shall not exceed 18 times. 7
GB/T4827—1984
Appendix B
Test method for circuit damage factors
(Supplement)
This appendix provides a unified test method for the tolerance of various transmission path damage factors specified in the standard. The accuracy of the instruments used must be calibrated with national secondary standard measuring instruments or devices. B.1 The measured circuit of the carrier audio channel (including the carrier voice channel and the transmitting and receiving voice trunk line) is shown in Figure B1. Points B and B are the transmitting and receiving points of the carrier audio channel respectively. Points C and C' are the four-wire input and output points of the carrier voice channel respectively.
Actuation
B.1.1 Net attenuation
a. Transmitting voice trunk line
2 i= g
Point B sends a 800Hz, 0dBm sinusoidal signal, and a low-frequency level meter is used to measure the attenuation value (dB) at point C. The attenuation value should be 14dB. b. Receiving voice trunk line
Point C' sends an 800Hz, 0dBm sinusoidal signal, and a low-frequency level meter is used to measure the attenuation value (dB) at point B, which is 4dB. c. Send a 800Hz, 0dBm sinusoidal signal at point B, and use a low-frequency level meter to measure the attenuation value at point B'. The attenuation value should be 0dB. The attenuation changes over time by taking the average of the attenuation values ​​tested in a month and calculating the standard deviation. B.1.2 Attenuation frequency characteristics
Send a 0dBm sinusoidal signal at point C, and measure the relative attenuation value relative to 800Hz at point C. The test frequency range is 300~3400Hz.
B.1.3 Random noisebzxz.net
Terminate a 600Q resistor at point B, and use a noise meter to measure the weighted noise level (dBmp) at point B'. Terminate a 6002 resistor at points C, B, and C respectively, and measure the weighted noise level (dBmp) at points C, C, and B respectively. These values ​​are the random noise levels (dBmp) of the carrier voice circuit, the transmitting and receiving voice trunk lines. B.1.4 Pulse noise
Connect a 600Ω resistor to point B, and connect a pulse noise counter (impedance 600Ω, no-load time 125ms*) to point B. Directly read the pulse noise count value. The test time is 15 minutes. The pulse counter threshold is -18dBm0. The level of the carrier four-wire receiving point (Figure B1, point C') is +4dBm. When measuring at point C', the pulse noise threshold level should be -14dBm. When the receiving level at point B' is 0dBm, the pulse noise threshold level measured at point B should be -18dBm. B.1.5 Frequency deviation
*The period from the start of the previous pulse to the time when the counter is ready to record another pulse. 8
GB/T4827—1984
Connect a frequency deviation meter (impedance 600Ω) to points B and B' respectively. At point B, use a frequency deviation meter to send two phase-related frequencies of 1020Hz and 2040Hz, and a sine signal of 0dBm level. At point B, read the frequency deviation value (Hz) directly (positive or negative deviation). B.1.6 Single-frequency interference
Terminate a 600Q resistor at point B, and use a low-frequency frequency selector (impedance 600Q) at point B to measure the maximum single-frequency interference level (dBm) in the frequency band of 300 to 3400Hz.
B.1.7 Power supply interference
Send a 800Hz (or 1020Hz) 0dBm0 sine signal at point B, and use a low-frequency frequency selector at point B to measure the maximum value (dBm0) of the 800±n·50Hz (or 1020Hz±n·50Hz) side frequency component. a. Crosstalk protection degree of receiving and transmitting
Send 800Hz, 0dBm0 sinusoidal signal at point C of the transmitting branch, and terminate at point C with a 600Q resistor. Terminate at point B of the receiving branch with a 600α resistor, and use a level meter to measure the crosstalk level at point B (near end). The difference between the measured dBm0 value and 0dBm0 is the crosstalk attenuation. Since the net attenuation of the circuit is 0, this value is the crosstalk protection degree. b Crosstalk protection degree between adjacent voice channels
Send 0dBmO sinusoidal signal at point C of the transmitting branch of the main crosstalk voice channel, and use a frequency-selective level meter to measure the crosstalk level at point C of the receiving branch of the crosstalked channel. The difference between the measured dBm0 value and 0dBmO is the crosstalk attenuation. That is, the near-end crosstalk protection degree. Similarly, connect the main string signal source to the sending end C' point of the receiving branch of the main string voice circuit, and measure the far-end crosstalk protection degree at the C point of the receiving branch of the received voice circuit.
The test frequency is the center frequency of the carrier reporting circuit. The influence of the noise in the circuit should be considered in the test. B.2 Solid line audio path
Light training design
Germany real money consultation card
The circuit under test is shown in Figure B2. Points B and B are the sending and receiving points of the solid line audio path respectively. B.2.1 Net attenuation
Receiving card
A low-frequency oscillator (impedance 600Q) is used to send a 3200Hz 0dBm sinusoidal signal at point B, and a low-frequency frequency selector is used to measure the attenuation value (dB) at point B'.
B.2.2 Random noise
The test method is the same as B1.3.
B.2.3 Pulse noise
Send a 3200Hz, 0dBm sinusoidal signal at point B, measure the receiving level at point B', and the pulse noise threshold level is 9dB lower than the receiving level. Directly read the pulse noise count value. Test time 15min. B.2.4 Single-frequency interference
The test method is the same as B1.6.
Additional Notes:
GB/T4827—1984
This standard was proposed by the Ministry of Posts and Telecommunications of the People's Republic of China and is under the jurisdiction of the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. The main drafters of this standard are Liu Huadong and Hong Lifen.
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