Electrical Experimenter, November, 1919, pages 708-709:

SEVEN  ZEPPELINS  WERE  LURED  TO  DEATH  BY  RADIO.

    This is the tale of the seven Zeppelins.
    Do you remember the last big raid over England after which most of the flock of ungainly birds came flopping down into the fields and forests of France, while one met its fate in the Mediterranean?
    People in London told one another all manner of tales about frozen motors and gasoline icicles. As well to let it go at that in those days, but now that I know the Germans know all about it here is what happened, says Gordon Stiles in a press report from Berlin.
    A certain French radio officer had been very diligent during the war. When America came in some wireless experts from over there joined forces with him. Among other things they studied the German method of wireless control of aircraft.
    The Allies had known for a long time the Zeppelins were guided by instructions sent from powerful wireless stations in Belgium and Germany. When its cargo of bombs had been disposed of the airship would flash back, "Where am I? And what course shall I take to reach home?"
    This call would be received by several German stations, indicating the direction from which it came. Thus by using formula which involved mathematical calculation dealing with intersections and the like the position of the Zeppelin could be exactly determined. The rest was easy. The compass course to be taken went thru the ether to the Zeppelin.
    By patient work the French radio officer had compiled a vocabulary which embraced more than 400 German code words. With the help of mechanicians he had built a wireless set which had all the characteristics of the German apparatus, even to "flaws."
    On the night of the raid in November 1917, this set was read for use. Fate was with the Allies, for when the Zeppelins were floundering at a dizzy height over London, the signaled replies from the German stations did not reach them. Static disturbances prevented the message carrying.
    The French stations were very busy. "Come this way." "Take this course." "Steer so many degrees east by south." These were the messages flashed over the new sending apparatus.
    From the Zeppelins, one after another came "O. K." And they came. They came so accurately that the French actually telephoned the various anti-aircraft stations the exact minute when they might expect a Zeppelin over their position. Allied night fliers were sent up in swarms to demolish those which the guns did not claim.
    We know their success. The big gas bags came tumbling into France or sailed wildly about, damaged and limping, until the airplanes finished them.
    Another dent in Fritz's wild war dream.