Sonic sunglasses

The sonic sunglasses were a device the Twelfth Doctor used to replace his sonic screwdriver after he abandoned it. They were worn as normal, black sunglasses with no visible difference to normal sunglasses. He used them to recall the TARDIS after it had been dispersed by the HADS "dispersal" function. He expressed concern that, whilst in the possession of Davros, they might have become scratched. (TV: The Witch's Familiar)

He wore them during his three week visit to Essex, 1138. He referred to them as "wearable technology". (TV: The Magician's Apprentice / The Witch's Familiar)

The Doctor used them again in the underwater base the Drum in the year 2119 to connect to the base's Wi-Fi to allow the base crew to view the trapped ghosts from his position. He also appeared to use them to scan the markings on the wall in an alien spaceship. (TV: Under the Lake) He later used them to project a hologram of his likeness as one of the ghosts and to erase the markings from everyone's minds. (TV: Before the Flood) The Doctor attempted to use them to scare a group of Vikings, only for their leader to snap them in half. Clara later recovered half of them and used them the trick the Mire into believing her to be a threat to avoid, but failed to prevent a conflict when Ashildr declared war against them. (TV: The Girl Who Died)

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