I've seen a thread on here about this already, but no one knew what the guy was talking about, and I haven't found anything on other websites. On the Kino Der Toten zombies map, there's at least five red fuse boxes (they look like the trap switches, but are smaller and blend in much more). If you knife or shoot these boxes, the lid swings open and you hear and see it fizzle/spark. I'm thinking this is some sort of secret because, one, it does something when you interact with it, and two, one is connected to the teleporter by the same type of wire that is connected to the round platform in the first room. My guess is this does something to the teleporter if you find them all, like make it so you don't need to link it each time. Has anyone else found these or heard anything about them?
keep looking, the boxes your talking of that i've seen are in these places. by the quick revive there is one beside the window closest to the teleporter, and one in the same spot on the opposite wall. Theres one on the floor in the room with the fire pit. (first room from lobby if you open the bottom door) theres two in the dressing room. and theres one more that i know of but i forgot where.
I think they are just interactive environment objects. They are in multiplayer as well and you can knife them and they open and fizzle. It's just something to add to the environment when bullets are flying, stuff breaks and what not...
But, I'll totally eat my words if someone solidifies that something special happens from them.
I've knifed every one I've come across and nothing happened, also used the teleporter a few times after that, I'm pretty sure they're just objects you can interact with with zero consequence to anything else, like slashing the windows on Veruckt.