[Stooky Bill]

From a transmission tech perspective, how do +1 channels work? 

Presumably most of the time they are literally a box which takes the live feed of the normal channel, delays it by 3600 seconds, and spits it back out for tx with a different DOG?

However does the broadcaster have the ability to break into this process, either at the box side or the tx side, with different content? I have seen before where, for rights reasons, the +1 has had to be blocked. Is this done at the box or downstream from this? Could broadcasters, if they chose to, put some completely different content up instead of the blanking?

Do any +1 broadcasters have a completely separate playout chain for their +1 channels instead of this delay box, where they could put different content/adverts/trailers on the +1 version?

Are the delay boxes located at the playout side (and require a separate uplink) or the tx side?

I'm not sure what you mean by that last sentence, what's your distinction between playout and TX? 

My understanding is that they basically record the channel onto a video server and then play it  back an hour later, just like your domestic PVR can. 

They'll just be a seperate output of the playout area, but one that comes from a single server port rather than a full playout suite. Everything downstream of that - the logo bug, EPG, encoding etc will probably be the same as the main channel. 

Obviously some reactive channels like ITV can replace the output of the +1 if need be. Presumably this will be just some sort of simple switcher to go between the server output and a caption. But yes that could be theoretically anything they wanted,

Potentially a +1 could be just the same schedule in a seperate playout chain just playing an hour later, but that's a lot more work and of course doesn't work with live content.