Not to be contrary, but I assure you, you DO NOT have an HTC Desire One X Plus, as that simply does not exist. The HTC Desire series & the HTC One series are 2 different product lines entirely. Don't take MY word for it: Google "HTC Desire One X Plus". Nothing comes up (Actually, there IS one site which displays an "HTC Desire One X Plus", but it is inappropriately labeled, as what they are selling is actually an HTC One X+, International Version:
MOX: online shopping for him and her. Adventure, Travel, Fashion, Gadgets & beyond | HTC Desire One X Plus ). Go to HTC's website, and see if you can find any mention of an HTC Desire One X Plus. Nothing comes up. You have one of the following:
• an HTC Desire:
HTC Desire - Wikipedia, the free encyclopedia (I'm guessing No, though)
• an HTC Desire X:
HTC Desire X review: one last hurrah for a former flagship? (Possible)
• an HTC One X:
HTC One X Overview - HTC Smartphones (also possible)
• an HTC One X+ (sounds like the International version, as the lights at the bottom of yours are red):
HTC One X+ review: it's the One X, and then some (video) (most likely)
Revised opinion: I actually think you have an HTC One X+, International Version. Your mention of the red lights indicates this. And you've not done badly, because it's a great phone. As for when the lights activate, I can only speak of my own experience with a One X+ (I own one), and in my experience, they do not come on/stay on in low light conditions. They come on when used, and stay on for a bit, but then turn themselves off (presumably to save battery life). I've not seen them behave otherwise. If there is a way for them to activate based on light conditions, I'm not aware of it.
Hope this helps. If you need manuals, I've got them, in pdf format. But they're for the American LTE version (AT&T). Just let me know. I'd be happy to send them to you.
Best of luck.
~Hjortron