Transmat capsules were a variation of transmat technology that allowed beings to move from one point to another. Just like normal transmit capabilities, it had a limited range within it could travel.
The capsule enhanced the capacity of the matter conversion system by providing additional computing power. Capsules also offered protection should the location being transmatted to be dangerous. (TV: Mawdryn Undead)
The Nimons' travel capsules, which could hold about three Nimons, worked in a similar matter. Their power complexes were reminiscent of giant transmats, creating gravity wells that collapsed into an artificial black hole and sent their capsules through hyperspace for inter-planetary travel. (TV: The Horns of Nimon) At some point the capsules had directional units that allowed them to travel through space. (AUDIO: Seasons of Fear)
Transmat capsules existed in the 30th century (AUDIO: Cobwebs) and were either used by or known to the Earth Empire in the 34th century. (PROSE: The Dark Path) They were also known by some in the former Drashani Empire, which existed around the time of the Earth Empire. The Doctor's TARDIS was thought to be a transmat capsule. (AUDIO: The Shadow Heart)