Possible reasons: the power supply is not stable;
Processing method: test system power supply, look to whether stable, adequate
Possible reasons: extension problem;
Processing method: check the extension of the contrast and brightness adjustment.
Possible reasons: the video signal is not stable;
Methods: using the multimeter, signal detection system, look to whether stable, adequate; Special circumstances building visual intercom system used alone video distribution amplifier, please view the video distribution amplifier regulator, whether regulation is normal.