TARDIS Communication Network

Um... I know this might sound like a bit of an odd request, but... I was just starting my Mechanical Engineering training... anyone here know anything about it that would be willing to let me train under them?

Does anyone know how long the battery lasts on these tablets?
This whole...power flickering thing has me freaked out.
If there's no lights, and my tablet dies, how the hell am I supposed to get in contact with anyone?

Okay, you know all those power outages and cuts and stuff? I swear it wasn't me. Honest to God. I mean, this time. If it happens and it is my fault, I'll admit to it. But this time... I honestly have no idea what's going on. Does anyone know?