A system for detecting a digital camera failure captures an image with the digital camera. A system for hierarchical link aggregation may include a network interface having a plurality of physical ports. The compression space and expansion space are in fluid communication with, respectively, a compression piston and an expansion piston, and the separate Stirling cycle units are mechanically coupled together by linear power transmitters, which connect the expansion piston of one unit to the compression unit of the other. The application specific logic is to determine a group of routed interfaces and an associated set of ports for each routed interface based on the route group identifier.