The Claws of Axos standard. The story includes interior scenes inside the TARDIS for the first time in the Pertwee era of the show. The configuration of the TARDIS set-up is unique for this adventure. The TARDIS monitor appears to be a circular screen embedded in one of the 'roundels' in the console room wall, rather than the traditional rectangular screen (this feature is seen again once, a year later, on the unique set built for "The Time Monster"). The doors of the console room do not open directly into the exterior as in all other adventures; instead they open into a corridor that
Working fluid Working fluid A working fluid is a pressurized gas or liquid that actuates a machine or heat engine. Examples include steam in a steam engine, air in a hot air engine and hydraulic fluid in a hydraulic motor or hydraulic cylinder. More generally, in a thermodynamic system, the working fluid is a liquid or gas that absorbs or transmits energy. The working fluid properties are essential for the full description of thermodynamic systems. Although working fluids have a very large number of physical properties which can be defined, the thermodynamic properties which are often required in engineering design and analysis