A spacer material is provided for a field emission display with a cathode plate having a plurality of electron emitters. In one embodiment, a flight deck panel illumination system includes at least one illuminated panel having at least one illumination source, and a power supply coupled to the at least one illumination source and to an electrical energy source that is configured to selectively provide a suitable power conversion mode in response to an applied signal. When the pump shaft rotates in a forward or reverse direction, the pistons reciprocate to supply hydraulic oil sucked from a tank to a suction port of an operation control valve. Alternatively or additionally, the customer may access a loyalty program without needing to provide a physical card or data associated with a card. The first gain level is a level of gain that results in effective cancellation of sounds transmitted through or around the ear cup and through the user’s head, and the second level is a level of gain that is matched to the level of sound of a typical wearer’s voice transmitted through the wearer’s head when wearing the headphone.