Editing Instrument landing system (section)

===Beam systems===
{{main|Lorenz beam}}
Previous blind landing radio aids typically took the form of ''beam'' systems of various types. These normally consisted of a radio transmitter that was connected to a motorized switch to produce a pattern of [[Morse code]] dots and dashes. The switch also controlled which of two directional antennae the signal was sent to. The resulting signal sent into the air consists of dots sent to one side of the runway and dashes to the other. The beams were wide enough so they overlapped in the center.<ref name=hist>{{cite web |url=http://www.radarworld.org/flightnav.pdf |title=History of Radio Flight Navigation Systems |website=Radar World |pages=2–4}}</ref>

To use the system an aircraft only needed a conventional radio receiver. As they approached the airport they would tune in the signal and listen to it in their headphones. They would hear dots and dashes (Morse code "A" or "N"), if they were to the side of the runway, or if they were properly aligned, the two mixed together to produce a steady tone, the ''equisignal''. The accuracy of this measurement was highly dependent on the skill of the operator, who listened to the signal on earphones in a noisy aircraft, often while communicating with the tower.<ref name=hist/>

Accuracy of the system was normally on the order of 3 degrees in azimuth. While this was useful for bringing the aircraft onto the direction of the runway, it was not accurate enough to safely bring the aircraft to visual range in bad weather; the radio course beams were used only for lateral guidance, and the system was not enough on its own to perform landings in heavy rain or fog. Nevertheless, the final decision to land was made at only {{convert|300|m}} from the airport.<ref name=hist/>