Callisto Pulse

A Callisto Pulse was a device of sorts that could disarm micro-explosives from within up to 20 feet. River Song offered the pulse to Dorium in exchange for a vortex manipulator, it was required by Dorium to disarm the micro-explosives that he had drunk from his glass of wine. The Pulse was in the form of River's earring. (DW: The Pandorica Opens)