What are the possible reasons for reporting BUS_ERR among the following options (multiple choices)

• A.OOF (loss of clock: clock, frame header jitter; no clock board inserted)
• B.Receive FIFO overflow (clock, frame header jitter; no clock board inserted)
• C.LOS (The channel of the service board or cross-connect board is not opened; the pin is reversed, and the board is not inserted tightly)
• D.LOF (same as LOS; clock loss; business slot physical slot and logical slot are inconsistent)

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Hybrid MSTP devices support inter-domain (packet domain, TDM domain) intercommunication, which of the following descriptions is correct? (multiple choice)

• A.TDN services are carried by end-to-end packets
• B.Packet services are carried by end-to-end packet
• C.Packet services are carried by end-to-end SDH
• D.TDM services are carried by end-to-end SDH

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Which of the following is not an antenna parameter?

• A.3db beam angle
• B.Front-to-back ratio
• C.Antenna gain
• D.Standing Wave Ratio

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Which of the following is the error about the optical power commissioning?

• A.The actual gain upper threshold of an OAU is smaller than the nominal gain upper threshold, indicating that the performance of the OAU board is degraded and it is recommended to replace it.
• B.For 10G and 2.5G systems, adjust the received optical power of the wavelength conversion board to "high 3 low 5", which is 3dB higher than the receiving sensitivity and 5dB lower than the overload point.
• C.Adjust the VOA (adjustable optical attenuation) in front of the optical amplifier board so that the input optical power of the board = the input single-wave nominal optical power + 10lgN, where N is the actual wave number. If it is not adjusted to the nominal value, adjust the VOA attenuation to the minimum.
• D.Adjust the OAU gain of the optical amplifier board to make the output optical power reach the standard.

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In the point-to-point WDM networking scenario, the signal-to-noise ratio of a certain single wave is low, and the other channels are normal. The reason is that it is impossible?

• A.The attenuation of the pigtail from the OTU board corresponding to this wave to the multiplexer increases
• B.The transmit optical power of the OTU board corresponding to this wave has decreased
• C.The gain slope of the amplifier changes
• D.Increased attenuation on the light path

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