The C20 series cameras and other Topview cameras can have a DC offset that when used with third party UTP systems such as NVT causes video and /or coaxitron communication issues.
Pelco Cameras, Pelco Video Management, Pelco Transmission & Power
When using C20 or other topview cameras and third party UTP systems
The DC offset causes differences in the amplitude of the video and /or coaxitron. NVT compensates for this by using a blocking capacitor or a terminating resistor of 200 to 1000 ohms.
Use a blocking capacitor or terminating resistor of 200 to 1000 ohms. NVT has a blocking capacitor set up you can buy from them for this. Be careful that in using this you do not block out coaxitron signaling. You may to put an oscilloscope on the line to see what the result of adding this capacitor would be.
View the NVT product of NV-DCI4 here: NV-DCI4
Note: The product is application specific towards UTP equipment installed.