A sonic gauntlet was a type of sonic device, one of which was used by Paternoster Gang member Jenny Flint. She wore it on her left arm.
Very soon after a Tyrannosaurus rex was accidentally brought to 1890s London, Jenny used her sonic gauntlet to scan the dinosaur, finding that the creature seemed to have something lodged in its throat; what she was detecting was the Twelfth Doctor's TARDIS. (TV: Deep Breath)
Behind the scenes
Jenny Flint's sonic gauntlet was one of three props (all of which were sonic devices used by the Paternoster Gang) that resulted from a Blue Peter competition. The sonic gauntlet was designed by a thirteen-year-old boy from Somerset named Connor. His design included a tumbler to make locks fall apart, a radioactivity measurer and receiver dish, and a watch that showed the conductivity of metal in a lock. Steven Moffat, who helped judge the competition, commented, "We love this because it looks really cool; it looks quite steam punk – it looks Victorian, but looks technological at the same time and I can just imagine Jenny Flint when she goes out in the morning needing something like that on her arm." [1] In the stage directions from the script of Deep Breath, the device was simply described as Jenny's "hi-tech gauntlet," rather than mentioning it being sonic in nature.