What we are doing is one line straight to the Lindy from the PC, a separate line from the Apple TV, via a Kanex box, VGA, to the Lindy, with the Lindy then putting a single line to a separate powered VGA splitter, which goes off to the PC monitor and then off to the projector. To complicate things we have more than one AV solution in the system. Some have a SmartBoard solution, with integrated control panel, but with various versions of the control panel set up implemented. Some with a Promethean set up, with separate audio and visual output. The Promethean's have an issue where the Epson projector can't make up it's mind whether it is going to be an PC projection or an ATV selection (keeps jumping between the two)l. Have added a PSU to one of the Lindy boxes, it stops the jumping between the two devices but prioritises the PC. Does not allow the ATV unit more than 3 seconds of connect time before reverting back to the PC.
Must apologize for the grammar and information in this reply,just returned from a Royal Engineers Association Branch Meeting, where beer is a standard form of communication, and I drink Guinness.