220-SIG Tactical Sensor Jamming Device
From Wookieepedia, the Star Wars wiki.
The 220-SIG Tactical Sensor Jamming Device was a Kuat Drive Yards designation for a powerful jamming system that was produced for the Galactic Empire. They were used as a form of electronic warfare system by preventing the use of sensors as well as blocking all communications in the given area.
Hundreds of such devices were known to be present on the Death Star.
