Videoscopes were a technology the Daleks used on Skaro to monitor the situation around their city. They were created after the Monstrons' attack. (COMIC: Eve of War) They were also used to watch prisoners. (TV: The Daleks)
The Dalek Supreme, immobile in the city's subterranean levels, used videoscopes to monitor activity in the city above, possessing a special code to remotely activate them. (AUDIO: Return to Skaro) At the onset of the Thal-Dalek battle, the First Doctor and Susan Foreman destroyed one of the videoscopes when sabotaging a static electricity junction box. (TV: The Daleks)
Fifty cycles after the battle, the Supreme identified a returned Susan through the videoscopes, ordering all surveillance resources to be placed on her, causing the Daleks to be caught unaware by a later party of intruders. After identifying the Doctor and Ian Chesterton, the Supreme ordered all videoscopes to focus on the Doctor. When the Supreme's attendants left for the Thal City, it remotely activated the videoscopes to monitor the Doctor. After the Doctor and Tryana had been captured, the Supreme mockingly turned the videoscopes to the activating Dalek army. (AUDIO: Return to Skaro)
The World Space Patrol ship Fireball XL5 had a videoscope. In January 2065, Professor Matic used it to identify the craft they were fast approaching as a space freighter. (COMIC: The Batmen)