I have been asked several times about the relay that I have behind my TV that operates the projector screen and PC buttons. So here is an annotated photo to help explain it better. The 12V power for it is actually routed down from the loft so it works even when the spur in the lounge is off. This is so I can turn the PC on without having to turn the spur on.

This pre-assembled relay from Quasar Electronics has jumpers so that each relay can either latch or be momentary. For the screen and LED lights it must be set to latch, and for the PC buttons to momentary. You can click on this image for a larger version

Then inside the PC in the attic, the 4 core cable is spliced to the power and reset cables respectively.

And then the little RF remote works for me as follows from the comfort of my sofa…

…and this is the relay as it comes (pre-assembled model) from Quasar