The core components of the Liberty system inlclude a System Electronics Unit (SEU), one sensor, and one source. The SEU contains the hardware and software necessary to generate and sense the magnetic fields, compute position and orientation, and interface with the host computer via RS-232 or USB. The Source contains electromagnetic coils enclosed in a molded plastic shell that emit magnetic fields. The source is the system’s reference frame for sensor measurements. The sensor contains electromagnetic coils enclosed in a molded plastic shell that detect the magnetic fields emitted by the source. A lightweight, small cube, the sensors position and orientation is precisely measured as it is moved. The sensor is a completely passive device having no active voltage applied to it.