Bomber crews already had some experience with these types of systems due to the deployment of the Lorenz beam, a commercial blind-landing aid which allowed aircraft to land at night or in bad weather. The Germans developed the short-range Lorenz system into the Knickebein aid, a system which used two Lorenz beams with much stronger signal transmissions. The concept was the same as the Lorenz system. Two aerials were rotated for the two converging beams which were pointed to cross directly over the target. The German bombers would attach themselves to either beam and fly along it until they started to pick up the signal from the other beam. When a continuous sound was heard from the second beam the crew knew they were above the target and began dropping their bombs.