(September 2014). A general sales agent (GSA) is a sales representative for an airline in a specific country or region. Typically, the GSA is responsible for selling all products of the airline in its region which includes flight tickets and cargo space. A GSA will typically sell the product of more than one airline.
Definition of standing wave. : a single-frequency mode of vibration of a body or physical system in which the amplitude varies from place to place, is constantly zero at fixed points, and has maxima at other points.
Vibration inside a tube forms a standing wave. A standing wave is the result of the wave reflecting off the end of the tube (whether closed or open) and interfering with itself. When sound is produced in an instrument by blowing it, only the waves that will fit in the tube resonate, while other frequencies are lost. The longest wave that can fit in the tube is the fundamental, while other waves that fit are overtones. Overtones are multiples of the fundamental.