An unnecessary strike of genius...
What is the tvLINK?
The TVLink, also known as the Magic Eye was a very clever accessory that Sky marketed shortly after the launch of Sky Digital since Sky Multiscreen was not a thing yet. It was still used many years later, after Multiscreen was launched, since people did not want to pay extra for their Sky TV subscription.
How does it work?
To use tvLink, you need to head over to Installer Setup on your Sky box and turn on the RF Output Power Supply. Now, you can plug in the tvLink. You need to plug the tvLink into the RF2 output on the back of your Sky box, and the output cable from the tvLink into the aerial port of your secondary TV. Next, you need to place the tvLink remote sensor somewhere near your second TV (most preferably the top). Once you've done this, you need to scan for channels (both digital & analogue) on your second TV and it should see the video coming from your Sky box through the tvLink. Add this channel to your secondary TV's EPG, and you can now watch from your Sky box on a second TV. To control it, just point your Sky remote at the sensor and it should work.