indicator that could listen to the signals and display the direction to the runway centerline as an arrow telling the pilot which direction to turn. The indicator also included two neon lamps to indicate when the aircraft crossed over each of the marker beacons. Later derivatives of the system had signals of equal length in the pattern left-right-silence, to operate a visual indicator in the cabin. The Lorenz system was similar to the Diamond-Dunmore system, developed by the US Bureau of Standards in the early 1930s. Use for blind bombing In the Second World War the Lorenz beam principle was used by the German Luftwaffe as the basis of a number of blind bombing aids, notably Knickebein ('crooked leg') and the X-Gerät ('X-Apparatus'), in their bombing offensive against English cities during the winter of 1940/41. Knickebein was very similar to LFF, modifying it only slightly to be more highly directional and work over much longer distance. Using the same frequencies allowed their bombers to use the already-installed LFF receivers, although a second receiver was needed in order to pinpoint a single location. The X-Gerät involved cross-beams of the same characteristics but on different frequencies, which would both enable the pilot to calculate his speed (from the time between crossing the Fore Cross Signal and crossing the Main Cross Signal), and indicate when he should drop his payload. The calculation was performed by a mechanical computer. Lorenz modified this system to create the Viktoria/Hawaii lateral guidance system for the V-2 rocket. Allied jamming effort When the British discovered the existence of the 'Knickebein' system, they rapidly jammed it, however, the 'X-Gerät' was not successfully jammed for quite some time. A later innovation by the Germans was the 'Baedeker' or 'Taub' modification, which used supersonic modulation. This was so quickly jammed that the Germans practically gave up on the use of beam-bombing systems, with the exception of the 'FuGe 25A', which operated for a short time towards the end of Operation Steinbock, known as the "Baby Blitz". A further operational drawback of the system was that bombers had to follow a fixed course between the beam transmitter station and the target; once the beam had been detected, defensive measures were made more effective by knowledge of the course. Sonne/Consol 'Sonne' (Eng. 'Sun') was a derivation of Lorenz used by the Luftwaffe for long-range navigation out over the Atlantic using transmitters in Occupied