PROPLAY88 This progressed into jamming techniques against individual German radar types and spoofing radars to see bomber streams that were not there. A more sophisticated method for blinding the German radar was "Mandrel", a jamming signal broadcast from aircraft accompanying the bomber stream or later certain bombers themselves. Just as the fighters reached the false stream, the "real" stream appeared hundreds of miles away, too far to be attacked. The British also attacked the communications between ground stations and fighters, with Operation Corona, broadcasting false directions in authentic accents over the radio. The British had held back from introducing Window for over a year lest the technique be adopted by the Germans and used against British cities.|How We Improved Our Slot {In one|In a single} Week(Month, Day)