New phone-jamming tech set for Supermax 2

Mobile phone-jamming technology will be trialled at a NSW high-risk prison in a bid to crack down on contraband.

Tests of the technology begins on Monday at "Supermax 2", a high-security unit for extremist-related offenders at Goulburn prison.

Authorities say the technology jams the frequencies that transmit mobile phone signals and follows a similar program implemented at Lithgow jail in 2013.

"Contraband mobile phones are an issue for prison authorities around the world, because the phones are as small as a key ring and can be easily concealed," Corrective Services NSW Commissioner Peter Severin said in a statement.

"This technology will make a significant improvement to the security at Goulburn because even if an inmate manages to smuggle a phone in, it will be completely useless for communication because it can't connect to the network."

If initial tests are successful, a two-year trial of the technology will take place.