https://apnews.com/6ae007ba40694bfe89f5f369fcf48e05

COLUMBIA, S.C. (AP) — Federal officials say they conducted a successful test earlier this year of a jamming technology some hope will help combat the threat posed by inmates with smuggled cellphones.

A report obtained Friday by The Associated Press details the January 17 test of micro-jamming technology at a federal prison in Cumberland, Maryland. Officials say they were able to shut down phone signals inside a prison cell, while phones about 20 feet away worked normally.