How long are the power cables from the adapter to the plug?

About 4 feet and they can be powered from either end.

Could you theoreticaly use a router to create more outputs? Has anybody tried it?

Common misconception. Routers and switches use Ethernet. Ethernet is a layer-2 protocol. Ethernet is not about the cable, but about the software. These boxes use Cat5/Cat6. Those are physical cables, not protocols. These do not use Ethernet, and therefore cannot be routed or switched. To sum up: Routers and switches use Ethernet > These VGA extenders don't use Ethernet > Therefore, you cannot send this signal through routers or switches.

compatible with gefen?

We are unable to confirm exactly which device you are referencing. The ST121UTPEP will work with any direct VGA source and VGA display. A loss of video signal and quality are common symptoms when video adapters and extenders are used in conjunction with each other. Atha, StarTech.com Support

StarTech.com VGA Video Extender over Cat5 (ST121 Series) - Up to 500ft (150m) - VGA over Cat 5 Extender - 2 Local and 2 Remote , TAA (ST121UTP)

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