Final answer:
A specialized tester used for testing COMBAT EDGE equipment, necessary for high-altitude or underwater situations, requires an external cylinder of compressed air or oxygen to function.
Step-by-step explanation:
The tester that tests COMBAT EDGE equipment and requires a compressed air or oxygen cylinder is likely a specialized device used by military personnel to ensure the proper functioning of high-altitude or underwater life support systems. This equipment might include oxygen regulators, masks, and other components critical for breathing in environments where regular atmospheric air isn't available or sufficient, such as at high altitudes or underwater.
Scuba divers often use compressed air from cylinders to breathe underwater, as depicted in FIGURE 9.16 and FIGURE 8.16. Similarly, military divers or aviators would use such equipment along with a tester to ensure that their breathing apparatuses are operating correctly before engaging in activities that rely on these life-support systems.
In training situations like those shown in FIGURE 11.11, where US Navy divers are seen in a recompression chamber or receiving hyperbaric oxygen therapy, the proper function of COMBAT EDGE equipment is crucial to safely simulate and counteract the effects of high-pressure environments. Therefore, a reliable testing device that requires external air supply (compressed air or oxygen cylinder) is essential for such operations.