Armed forces veteran Graham Moore, 66, pleaded guilty to three counts of downloading the illegal images onto his phone.
He was caught after police raided his home in Whitchurch on March 29 last year.
Telford Magistrates Court heard on Wednesday that the phone had one image of category A, the most serious type, two of category B and nine of category C.
Prosecuting, Katie Price said that Moore was jailed for six years for sexual offences against children in 1992.
After Moore pleaded guilty, chairman of the bench Nigel Atkinson said that the magistrates had decided they didn't have the powers to give Moore a strong enough sentence, after hearing of his previous offences.
They adjourned the case to Shrewsbury Crown Court for sentence, at a date to be determined.
In the meantime Moore, of Pauls Moss Court in Whitchurch, was made subject to an interim sexual harm prevention order, restricting his use of the internet, and told to sign the sex offender register.
Representing Moore, Kate Cooper said he suffered from post-traumatic stress disorder after a plane crash in Belize over 40 years ago.
She said that he came across the illegal pictures while searching for images relating to adult nudism, an interest of his.