Kontron tunnel

A kontron tunnel was a time corridor in space as opposed to the Time Vortex. Within the tunnel were projecting pentagonal lithoids that stretched out to oblivion, on the ends of which were kontron crystals. Removing crystals from a tunnel required skillful manipulation, otherwise removing them could cause instability and make the tunnel implode.

The Kontron crystals could be used to make small, portable time loops.

The tunnel appeared as swirling concentric rings, vortex attraction forces creating turbulent energies against things within the tunnel. The Timelash was a kontron tunnel utilised by the Borad. The Borad was tripped into the Timelash, and the Sixth Doctor destroyed it. (TV: Timelash, PROSE: Timelash)