A whistle was a device that made a shrill sound when its user blew air through it. The Alanciari, the Keshiri inhabitants of the continent Alanciar on the planet Kesh, used both personal whistles and larger, stationary whistles. The former type were used by soldiers to signal travelers to halt. The latter were mounted in population centers, where workers could funnel steam through them; the resulting sound served as a warning to the people nearby to stay alert to invasion by enemy forces.