Radio instrument approach and landing system

Claim 1

IN AN AIRPLANE RADIO INSTRUMENT GROUND TRACK GUIDANCE SYSTEM FOR USE WITH A PAIR OF GROUND-BASED OMNIDIRECTIONAL TRANSMITTERS OPERATING SUBSTANTAILLY CONTINUOUSLY AT DISTINGUISHABLY DIFFERENT RADIO FREQUENCIES, ONE SUCH TRANSMITTER BEING LOCATED AT THE FAR END OF THE LANDING FIELD RUNWAY, AND SUBSTANTIALLY IN ALIGNMENT WITH THE CENTER LINE THEREOF, AND THE OTHER SUCH TRANSMITTER BEING LOCATED AT THE APPROACH END OF THE RUNWAY AND DISPLACED LATERALLY FROM SAID RUNWAY SUBSTANTAILLY ON THE LINE OF THE RUNWAY "FENCE," THE COMBINATION COMPRISING AUTOMATIC DIRECTION-FINDING RECEIVER MEANS TUNABLE TO EACH OF THE TWO DIFFERENT GROUND-BASED TRANSMITTER FREQUENCIES, FIRST AND SECOND PICTORIAL DEVIATION INDICATORS HAVING A MAGNETIC BEARING INDICATOR ELEMENT, A BEARING REFERENCE SOURCE OPERATIVELY CONNECTED TO SAID ELEMENTS TO INDICATE MAGNETIC BEARING, EACH OF SAID INDICATORS HAVING A RELATIVE RADIO BEARING INDICATOR ELEMENT CONNECTION TO SAID AUTOMATIC DIRECTION-FINDING RECEIVER MEANS TO INDICATE RELATIVE BEARING OF THE AIRPLANE TO THE FIRST OF SAID TRANSMITTERS, SAID FIRST INDICATOR HAVING A LATERAL DISPLACEMENT INDICATOR ELEMENT