The Image Reproduction Integrating System, also known as the IRIS, was a device capable of translating thoughts into pictures. The Third Doctor had access to one when he worked for UNIT. He used it on Professor Herbert Clegg to confirm he had telepathic powers. The Doctor and the Brigadier used it to view Clegg's visions of Drashigs and giant spiders. (TV: Planet of the Spiders)
IRIS was similar to the device the Second Doctor used to project his thoughts on the TARDIS scanner. (TV: The Wheel in Space) It appeared similar to, but presumably was less advanced than, the Time Lord Thought Channel. (TV: The War Games)
The Fifth Doctor used it to analyze jelly-like substances that had been washing up at Tayborough Sands. (PROSE: Deep Blue)
Evidence suggested that Jeremy Fitzoliver accidentally activated the IRIS when he paid UNIT a visit while the Doctor was dealing with the Spiders. Exposure to the device virtually completely stripped Jeremy of his memory — he later adopted the alias "John Doe" — and he became a pawn of various psychic aliens trying to escape their prison dimension; "Doe" was no longer able to learn new information and his mind was unreadable by human telepaths. (PROSE: Instruments of Darkness)