What is the purpose of the MEM special function switch on the RMU?

The MEM special function switch on the RMU (Radio Management Unit) is specifically designed to recall the last used preset channel. This function allows pilots to quickly access their most recent communications setup without having to manually search through the memory channels. By pressing this switch, the RMU retrieves the previously used frequency, streamlining the process of switching back to a familiar or important channel during flight operations. This rapid recall feature enhances situational awareness and efficiency for pilots, particularly in dynamic scenarios where communication may change frequently.

The other options, while related to memory management, do not accurately represent the specific function of the MEM switch. The ability to reset all memory channels or to clear user settings involves different operational elements of the RMU and pertains more to its configuration or initialization rather than recalling past settings. Loading emergency frequencies is also a distinct function, typically associated with dedicated switches outside of the MEM function.