Identity check machine
From Tardis Wiki, the free Doctor Who reference
Identity check machines were a piece of Dalek technology.
They were created as an answer to the tendency of human agents to infiltrate Dalek flying saucers by climbing into Dalek casings and posing as Dalek soldiers. They made metal temporarily transparent; hence, all that was needed to verify the identity of a given Dalek soldier was to make it glide through the machine, and its driver (whether a Dalek mutant or a humanoid) would be made visible. (PROSE: Inside a Skaro Saucer)
