A reference model simulates a desired response characteristic of the variable valve timing apparatus and is constructed by using a dynamic characteristic in a region of the maximum changing speed of the valve timing of the variable valve timing apparatus. The encoder determines plural parameters for representing individual physical channels of the group as modified versions of the encoded combined channel. Global maps can also be made by using geographic location information associated with various local maps to fuse together multiple local maps into a 3-dimensional global representation of the field scene. The unit is compatible with a plurality of refrigerant types without cross-contamination of the refrigerant due to the oil-less compressor and conversion cycle whereby the vacuum pump is activated to remove residual refrigerant from the unit. The inputoutput ratio assembly has a first portion that is in rotational communication with the input assembly and a second portion that is in rotational communication with the output assembly.