It had directed beam weapons and was controlled by a direct link with the operator's brain. The TSS was also capable of functioning autonomously with a simple program — such as "Return to base", for example. The expedition to Deva Loka was outfitted with one TSS.
The machine had been used previously by two members of the expedition named Stone and Carter (PROSE: Kinda) to explore the area, but both disappeared without trace. Another called Roberts had also recently been in the TSS, but had also gone missing; the machine was empty when first discovered by the Fifth Doctor and Adric. When Adric impulsively shut the TSS's door, the machine activated and marched him and the Doctor to the expedition's domed base.
Later, Adric used the TSS to defend against the Mara-possessed Aris's attack, but was unable to control it effectively and his fear made its weaponry activate. The machine fired upon the Kinda and they fled. (TV: Kinda)
Shortly after the TARDIS left Deva Loka, Adric received a telling-off from the Doctor for being so reckless with the TSS, as the entire Kinda tribe could have been wiped out as a result. (TV: The Visitation)