Provided is a clock operating method and apparatus for supporting a plurality of Ethernet physical layer interfaces. Multiple communication addresses are stored in memory and associated with one or more inputs of the same input key, for example a first telephone number is associated with a single input of a key, and a second telephone number is associated with two sequential inputs of the same input key as the first telephone number, etc. Each of the upper element, intermediate element and lower element comprises a region of porous biocompatible material coated or impregnated with material having relatively high osteoconductive and osteoinductive properties. In this manner, a variable speed drive compressor can be operated at an extremely low speed to precisely match load demand on a refrigerant system. To facilitate portability, the keg cup holder is preferably constructed of an inexpensive and lightweight yet robust material. The surface of the foamed polymer layer is treated to make the surface hydrophobic.