Вот интересный отрывок из книги о навигации через "радио луч":
"I was fascinated with the business of learning to fly a radio beam.Lieutenant Herbine went into all th mechanics of how a beam works with four open quadrants
in each of which a code letter A or N can be heard. These quadrants are bounded by four legs of the beam formed where the
quadrant letters overlap each other.Since the signal for an A is a dot and then a dash, and the signal for an N is a dash and then a dot, the natural result of superimposing one over the other is the transmission of a steady hum over your radio reciever.."
"Bomber Pilot", Philip Ardery