Isotonic exercises involve moving your joints and muscles rhythmically and repetitively through their ranges of motion using low resistance, while isometric exercises are static and require you to contract your muscles without joint motion.
Substations are normally outdoors and are enclosed by a wire fence. However in residential or high density areas, the substation may be indoors and housed inside a building to restrict the humming noise of the huge transformers. slide 2 of 6 View of a Substation
Subversion is a centralized system for sharing information. At its core is a repository, which is a central store of data. The repository stores information in the form of a filesystem tree - a typical hierarchy of files and directories.