In the context of engineering, communications and electronics, especially military, a transportable device or system that can be can be moved quickly by truck, cargo aircraft, or other field vehicle, but is not mobile (i.e., cannot operate "on the move" (OTM)). A transportable system might be built into trucks or trailers from which it always operates, or be designed to be taken apart and placed into a set of shipping cases.
In the U.S. and allied AN- designation system for military electronics, transportable device designations, such as AN/TTC-39, start with the letter "T". As with the AN/TTC-39, there might be several trailers that need to be cabled to one another, and to support equipment such as antennas and generators. Other systems, such as the Joint Network Node, can be either vehicle mounted or be broken into shipping cases.