 Each post had its own code name and number.When aircraft were spotted, the volunteers would record their observations on forms or in log books and then quickly place a call to a regional Army Filter Center and verbally deliver a "Flash Message" which contained the organized data from the observation.One can imagine that aircraft approaching the coast would be spotted by multiple posts, resulting in multiple Flash Messages and, therefore, a reasonably accurate triangulation of position, speed, direction, altitude, etc.