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 and formulation of maintenance standards for transmission data communication systems. GB/T 4958.4-1988 Measurement methods for equipment used in ground radio relay systems Part 2: Measurement of subsystems Section 1: General GB/T4958.4-1988 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
GB/T4958.4—1988
idtIEC487-2—1:1981
Methods of measurement for equipment used inTerrestrial radio-relay systemsPart 2:Measurements
For sub-systems Section One-GeneralPromulgated on March 28, 1988
Implementation on February 1, 1989
Ministry of Posts and Telecommunications of the People's Republic of China
National Standard of the People's Republic of China
Methods of measurement for equipment used inTerrestrial radio-relay systems
Part 2:Measurements for sub-systems Section One-General inTerrestrial radio-relay systems Part 2: Measurements
For sub-systems Section One-General UDC621.396：621.317.08
GB/T4958.4—1988
IEC487—2—1(1981)
This standard is one of the national standards "Measurement methods for equipment used in terrestrial radio-relay systems" series of standards. This standard is equivalent to the International Electrotechnical Commission (IEC) standard 487—2-—1(1981) "Measurement methods for equipment used in terrestrial radio-relay systems Part 2: Measurement of sub-systems Section 1-General" 1 Purpose
The purpose of this standard is to determine the measurement methods for evaluating the electrical characteristics of various sub-systems, so as to facilitate the comparison of the results measured by different observers. The various measurement methods described in this standard can be used for "finalization" test and "acceptance" test. It can also be used for factory tests. 2 Scope of applicationbzxz.net
The measurement methods described in the following clauses of this part are applicable to all subsystems, including those parts that are not simulated systems (e.g., antennas). These measurement methods are used to evaluate the electrical characteristics that affect the performance of radio-relay systems and should be used in conjunction with Part 1 of this series of standards: "Measurements common to subsystems and simulated systems". This standard does not specify the values ​​of the measured parameters, as they should be given in the detailed equipment specifications. 3 Choice of test methods
The quantitative performance of various complete systems and their characteristics at international switching points are specified in the relevant recommendations of the International Radio Consultative Committee (CCIR). Since different arrangements of subsystems may meet the overall system specifications, they involve a wide variety of electrical characteristics and corresponding measurement methods. Therefore, it is often impossible to recommend a single preferred measurement method. However, the measurements described in Part 2 of this standard should, in all cases, at least be able to evaluate the basic electrical characteristics of the subsystem. 4 Definition of subsystem
A subsystem is defined as a combination of circuits and devices that can perform a specified function (e.g., modulation, RF branching or multi-channel switching) and have specified electrical, mechanical and environmental characteristics. 5 Test conditions
Generally, the standard test conditions in Section 1 of Part 1 of this series of standards shall apply. However, for some subsystems not included in Part 1 (e.g., antennas and passive redirectors), different test conditions may be used and refer to the corresponding sections of this part. Approved by the Ministry of Posts and Telecommunications of the People's Republic of China on March 28, 1988 and implemented on February 1, 1989
Additional notes:
GB/T4958.4—1988
This standard is under the jurisdiction of the Post and Telecommunications Industry Standardization Research Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the Post and Telecommunications Industry Standardization Research Institute of the Ministry of Posts and Telecommunications. The main drafter of this standard is Liu Yunhai.
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