One embodiment of the present disclosure is directed to a mobile X-ray unit. The clock input sub-circuit includes a first clock signal terminal and a second clock signal terminal. The filter media exhibits a machine-direction tensile strength of at least about 105 lbin, and a cross-direction tensile strength of at least about 110 lbin. The method includes transmitting, from the node of the cellular radio network, the request to the at least one user equipment. Once a wax tree assembly is completed a new wax runner replaces the wax runner that has been formed into a wax tree and additional wax runners are affixed in the same manner. The apparatus comprises an area in which said device is to be heated and inlet means adapted to supply a relatively inert gas to the said area.