When you are using this HDMI over CAT extender is it needed to use both cables is you are only sending survaillance video and no sound?

Or are both cables needed for Power at the receiver side? Or would 2 power supplies fix this issue?

Hello Pilotit and thank you for your interest in our Community.

I would like to confirm that both Ethernet cables are indeed required for the use of our ST121SHD50 HDMI extender. One of the cables transfers the raw video feed while the other does not only Power and Data, but also vital connection information between the two sides. This is why, when testing, you may end up with a working signal from using only the Video cable: but this will stop working after a certain time or as soon as either side reboots.

To ensure proper usage of our device, please always use both cables at all time. You’ll also want to make sure that both cables are of the same type, quality and length.

I hope this helps! Please do feel free to contact us back again should there be anything else we could do to help.