Mississippi prison blocked 216,320 illegal calls last month

Phone companies prefer managed-access solutions to technology that jams all cell phone reception in a certain location, which they see as too blunt an instrument.

Steve Largent, president of the wireless association CTIA, said in a blog post on Friday that managed-access technology works more like "a scalpel."

After deploying the technology, a state jail in Parchman, Miss., blocked 216,320 calls last month.

People on jail premises who try to make a call with an unregistered cell phone get a fail message: "The cellular device you are using at the Mississippi State Penitentiary has been identified as contraband and is illegal to possess under the criminal statute, 47-5-193. The device will no longer function."

The technology, approved by the Federal Communications Commission, also makes call information available for analysis so officials can do a deeper dive into who is breaking the rules.

Largent said the technology allows officials "to identify the location of a contraband phone, track its use and provide opportunities to retrieve the device and prosecute those in possession."

President Obama signed a bill into law last month, championed by Sens. Dianne FeinsteinDianne FeinsteinDem: Trump's China trademark looks like a quid pro quo Senate advances Trump's Commerce pick Flynn told FBI he didn't talk sanctions with Russian envoy: report MORE (D-Calif.) and Chuck GrassleyChuck GrassleyRepublicans at risk in 2018 steering clear of town halls Iowa farmer warns Grassley about creating 'one great big death panel' with ObamaCare repeal Senate eyeing vote on Trump's Supreme Court nominee by Easter MORE (R-Iowa), that threatens a year of jail time to people who attempt to sneak phones to inmates.