“Off Tube” is when commentary for an event is provided by the commentary team just watching the televised pictures. While commentators almost always have a picture monitor (or “tube”) regardless of their location, there is great advantage to be had from also being in a position to see the proceedings with their own eyes, and arguably to better sense the occasion while being immersed within it.
Generally off tube commentaries are done for economic reasons, when for example significant foreign travel is involved. Physical limitations also apply; most golf commentary is effectively Off Tube, even if the commentators are actually at the golf course, as it is not possible to see the whole of a golf course well enough from one location. At major events, such as the Commonwealth or Olympic games, the various venues may be several hundred miles apart, and thus a small commentary team would not be able to travel between venues in time. At these major events Off Tube commentary facilties are provided at the International Broadcasting Centre (IBC).