An auto focus image system that includes a pixel array coupled to a focus signal generator. Restrictions on resource consumption are implemented to ameliorate stressing the network bandwidth or adversely affecting the quality of service guaranteed to tenants of the physical node. A connector element is connectible with a hot air source for delivering hot air into the bladder compartment for subsequent dispatch through the plurality of nozzles. The inner impact layer is attached to an inside surface of the helmet shell. In one example, the apparatus and method read the data back contemporaneous with writing of the data, and measure an amplitude of a readback signal and store, as the refresh indicator, a predetermined fraction of the measured value.