Possible reasons: the power supply is not stable;
Processing method: detection system power supply, see whether stable, adequate.
Possible reasons: extension problem;
Processing method: to see the extension of the contrast and brightness adjustment is normal.
Possible reasons: the video signal is not stable;
Processing method: using the multimeter detection system signal, to see whether stable, adequate; special circumstances under building visual intercom system used alone video distribution amplifier. Please check the video distribution amplifier regulator, adjust is normal.