A firmware update was recently released for the NVR6XX-4KS2 series devices.
Information, instructions, and download links can be found Here
From Dahua Wiki
I connect the general analog camera to the device, there is no video output.
There are following possibilities:
- Check camera power supplying, data cable connection and etc. There might not be sufficient power from the power source. You can use a voltage tester if you have one on hand.
- Check the length of cable run. Refer to the specifications for the limitations on the cable length.
- This series device does not support the analog camera of all brands. Please make sure the device supports general standard definition analog camera.
- If there is no video, check the coax connection. Unsecured faulty connections will result in no video or intermittent video.