A court heard Christopher Mosby was seen trying to hide items when prison officers went into his cell on August 6 last year.
-> The full list of roads closed in Leeds for the Tour de YorkshireMosby then handed over what appeared to be two small phones but denied committing any offences, claiming they were lighters.
Leeds Crown Court heard the two devices were examined by an investigator.
One was found to be a working phone. It did not contain a SIM card and was not capable of being charged using a conventional charger.
Duncan Ritchie, prosecuting, said the device was capable of being charged using the cable from a kettle. The other was found not to have any working internal parts and not to be a working phone.
-> Teenager planned to flood Leeds Festival with bags of fake cocaineMosby pleaded guilty to unauthorised possession of a device capable of transmitting or receiving images, sounds or information by electronic means.
Mosby was sentenced to seven years in September last year for robbery and other violent offences in Wakefield.
In one offence Mosby, of Lindsay Avenue, Lupset, threatened a member off staff with a fake gun during a raid on a betting shop.
Mosby fled with £175 but was arrested after a police officer recognised him from CCTV images of the raid.
Mosby also hit a man over the head with a pool cue during a disturbance at the Magnet pub, Dewsbury Road,
He was told he must serve a further eight weeks in prison for the phone offence.