Dual cable and sat boxes - how?

How do these boxes work? As in, i want to watch bbc one, how do I know which tuner I'm watching? Or does the box choose? if I say, for example, have a sat feed in one tuner and a cable feed in another - how do I choose a channel from either box??

I'm looking at a zgemma h1 if it helps!

On the info bar it will tell you what tuners are in use A, B or C, and you ull need 2 bouquets to have have both sat and cable lists, so if you choose a channel from the sat list then you are watching sat, cable list your watching cable

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