Outside broadcasting

, often abbreviated OB, involves video recording in any location other than a studio. Called "mobile" or "remote" broadcasting in the United States, it's typically facilitated through the use of a satellite truck in the 21st century. At the British Broadcasting Corporation, during the time of the 1963 version of Doctor Who, outside broadcasting was done by the Outside Broadcast department, leading some Doctor Who commentators to style the term with capital letters.

Overview
Though developed primarily for news and sports programming, OB video was occasionally used by the British Broadcasting Corporation to record dramas. Doctor Who was a program which sometimes used the technology, when the OB units weren't being used by BBC Sport.

The result of using OB video for location filming was that there was no obvious difference of media between studio and location work. In a typical episode of Doctor Who broadcast between season 1 and season 20, the location work was captured on either 16 or 35mm film, while the studio work was recorded on 2" quad videotape. Therefore, viewers experienced a somewhat obvious difference in media quality between studio and location work. The only time this didn't happen is when experimental approaches were taken, such as when the whole of Spearhead from Space was filmed, or when the location work on Robot was recorded on OB video.

After season 21, all Doctor Who was filmed on 1" Type C tape, and beginning with season 23, location work was, by policy of the production team, done on OB video.

Milestones

 * The first Doctor Who serial to have all its location work on OB video was Robot.
 * The first Doctor Who serial to be completely recorded on OB video was The Sontaran Experiment. The Curse of Fenric and Survival were the only other such serials. The Greatest Show in the Galaxy came very close, after an asbestos scare unexpectedly forced Doctor Who out of the studios.
 * Regular use of OB facilities for location work began with The Mysterious Planet.