Rangerscope

The rangerscope was a type of surveillance device used by the Daleks in their city on Skaro. (TV: The Daleks)

When the Daleks first isolated themselves in their city, they used their rangerscopes to chart nearby space but found no other life bearing worlds, leading them to validate the Kaled belief that only Skaro could support life. (AUDIO: The Lights of Skaro)

When Susan Foreman was sent out to retrieve the anti-radiation drug, the Daleks tracked her with the rangerscopes. At the onset of the Thal-Dalek battle, the Thals used light reflection to disrupt the rangerscopes, something the Daleks compensated for by rerouting power to them. When the First Doctor and Susan made their way to Section 15, the Daleks considered monitoring them via the rangerscopes but decided that the vibrascope was more suited to an ambush. (TV: The Daleks)

After their failed invasion of Islos, the Restoration Empire used rangerscopes to monitor the progress of an entity that had declared war on them. (WC: The Sentinel of the Fifth Galaxy)