The S-Series module features a standard two inch diameter circular interface, and is designed to be assembled without tools into robots of various configurations. For example, several of the single degree-of-freedom, series-elastic rotational joints can be connected into a serial chain to form a torque-sensing snake robot -- useful for crawling into and inspecting small, convoluted spaces which larger systems cannot access. These same modules can be attached to a "body" module, along with other "foot" pressure-sensing modules, to result in a quadruped or hexapod that can overcome taller obstacles and carry larger payloads.