Security camera
From Tardis Wiki, the free Doctor Who reference
The security camera was a hovering, wood covered, mechanical sphere that CAL used to observe the Library when she closed her eyes in her imaginary world. The Tenth Doctor called it "an alive one" after he forced it to reactivate with the sonic screwdriver and CAL reacted with pain. Whatever she said was shown scrolling across a small monitor on the sphere, causing the Doctor to put it down and apologise. A courtesy node later repeated the warning, "Others are coming". (TV: Silence in the Library)
