You read it right! I've found you a brilliant, unpowered HDMI signal booster that can repeat your 4K signal out to distances of 40 meters or more! The clever key to this smart adapter is that it uses your HDMI cable's own voltage (fed from the input) to power the signal repeater circuits! This means it's best to place it in the middle of the cable run, rather than near the devices it will link.
This is a passive HDMI Repeater. No power supply required!
How awesome is that? Now you can install your HDMI cables inside walls, floors and ceiling cavities - even on long runs - without a mains socket forever leeching power from your house! This In Line HDMI Repeater is only working when you need it to thanks to the plug-and-play nature of the device. It's also great when you're in a pinch to extend video output into another room or across a classroom or conference hall!
I've even gone to the trouble of checking that it's Ultra HD ready (from 480i through 1080p 3D all the way to 4K@30Hz!) with all the HDCP compliancy you could need. It's built to HDMI 1.4a specification, and of course it transmits your uncompressed audio along with your epic video signals, so you can get just about any two devices communicating fully through 24k gold pated connectors.
Now, I say 40m because that's what we achieved in our testing lab using a matching pair of Avencore Platinum Series HDMI cables, so if you're using another brand or cable quality, your mileage may vary. Image stability is also subject to environmental interference, so it may not be able to work miracles in some cases. It definitely beats a standard HDMI coupler, which failed the test.
Note: Daisy-chaining multiple repeaters is not supported or recommended and may not work as intended.