Police found 81 illegal pictures and videos when they seized two phones from David Cooper in November 2019.
Newcastle Crown Court heard an investigation of the devices also revealed he had distributed dozens of such images during conversations over the Telegrammessaging service.
Cooper, who has never been in trouble before, was released under investigation.
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The court heard in June 2020 officers paid him another visit and he claimed the only phones he had were still with the police.
But when an officer dialled a number the police had been told belonged to him, a phone started ringing from inside his mattress.
This time, a total of 454 illegal pictures and movies featuring children were found on the phone, as well as one extreme pornography image showing a womanhaving sex with a horse.
Cooper, of Dellfield Drive, Sunderland, admitted making and distributing indecent images of children, possessing extreme pornography and possessing a small amount of amphetamine found during the second raid.
The 32-year-old claimed he had been "duped" by a man, who had posed as a woman, into distributing the images.
But Judge Edward Bindloss said Cooper had "cold bloodedly" traded them and told him: "It seems to me you do have a sexual interest in children."
Judge Bindloss sentenced him to a total of 18 months behind bars.
Cooper must sign the sex offenders register and abide by a sexual harm prevention order for ten years.
Prosecutor Rachael Glover said police made the first visit to Cooper's address on November 12 2019.
On two mobile phones officers found 24 images and one video of category A, which is the most serious, 46 images and one video of category B and 9 imagesof category C.
Miss Glover said: "The age range of the children in those images ranged between four years of age and 15 years of age but the majority are of children between seven and nine."
Miss Glover said the Telegram messages showed Cooper had sent 40 images to one unknown contact, discussed trading images with another person and sent 31 videos to a third.
The phone seized on June 20, which was inside a mattress, contained 229 images and 23 videos of category A, 109 images and 14 videos of category B and 69 images plus ten videos of category C.
It also contained the extreme pornography image featuring the animal.