What is "teletank"

Teletanks were a series of wireless remotely controlled unmanned tanks produced in the Soviet Union in the 1930s and early 1940s. They saw their first combat use in the Winter War, at the start of World War II. A teletank is controlled by radio from a control tank at a distance of 500–1,500 metres, the two constituting a telemechanical group. Teletanks were used by the Soviet Red Army in the Winter War, fielding at least two teletank battalions at the beginning of the World War II on Eastern Front.