If you are getting a message on screen saying "Mode not Supported" or "Out of range" when connecting a DVR/NVR to a Monitor/TV then usually this will mean that the output resolution that the unit comes out on as standard is an unsupported resolution of the TV/Monitor.
On a Viper
For the Viper you will be able to press and hold down the right mouse button for around 10 second. This will cycle the DVR/NVR through its available resolutions until hopefully you end on a resolution that the monitor can support.
On a Quattro
On a Quattro, you will not be able to cycle through the resolutions using the right mouse button, instead there are two methods, the first will involve using a different screen (Preferably a smaller one) to get an image and once done, going into Main Menu > Encode > Display > Resolution and then changing the resolution to one supported by the monitor.
The second would involve connecting to the DVR via the network and logging into the DVR's IP address. Through the web client you again, go into the Display settings and change the resolution without the need for another monitor.