Drudger

The Drudgers were hovering machines primarily used as security drones.

On one planet, they reported back to Ruthley and assessed any visitors who stumbled across the hidden planet, also extinguishing fires. They would not kill unless provoked, remarking "that procedure is not permitted", but they did use an extremely painful mind scan on the Seventh Doctor and Elenya. They were then confronted by the assassins who had arrived to kill Sancroff, First Knight of Velyshaa; their firepower was useless against the assassins, and the Drudgers on the planet were presumably all destroyed. (AUDIO: The Sirens of Time)

Alby Brook's ship was equipped with a Drudger at the time of the Dalek invasion of Mutter's Spiral in 4162. (AUDIO: Invasion of the Daleks)

Space Dock Nerva was equipped with security Drudgers when it was visited by the Fourth Doctor and Leela. The Drudgers were armed with paralysis beams. (AUDIO: Destination: Nerva)