Reacting vibrator
From Tardis Wiki, the free Doctor Who reference
A reacting vibrator was a piece of equipment used by the First Doctor to make readings to help identify the planet he may have been on.
When he, Steven and Dodo landed on an Earth-like planet, the Doctor used it to take readings. When he encountered Edal and Exorse, they mistook it for a weapon. (TV: The Savages)
