for the first time on 23 February 1943 at Telefunken's offices in Berlin. A second example, also with a destroyed PPI, was captured on 1 March, ironically from a bomber that was part of a group attacking and greatly damaging Telefunken's offices, destroying the first example in the process. According to Lovell, interrogation of surviving members of the second crew revealed that: Combined with their own display, a set was reassembled on the Humboldthain flak tower in Berlin. When it was activated clear images of the city appeared on the display, causing considerable consternation for Hermann Göring. A quickly adopted countermeasure was put in place by installing small corner reflectors around the city, producing bright spots on the display in areas that would otherwise be empty, like lakes and rivers. Producing the reflectors with the required angular accuracy proved to be a difficult problem, as did keeping them in the right positions in order to produce the right image. Although the basic concept of the magnetron was immediately understood, a number of details of the system as a whole remained a mystery, and it was also realized that building a complete radar system using it would take some time. So for the short term, they gave "panic priority" to a ground-based jammer and a detector that would allow their night fighters to home in on the microwave signals. This development was slowed by the German electronic industry's decision to stop researching microwaves shortly before Rotterdam Gerät literally fell from the sky. Another serious problem was a lack of suitable crystal detectors that were key to the British receiver designs. Several jammer systems were trialled. The first, known as Roderich, was developed by Siemens. These used a transmitter mounted on a tower pointed at the ground, the reflections off the ground spreading the signal out in space where they were picked up by the H2S receivers. Roderich transmissions were timed roughly with the scanning speed of the H2S antenna, causing a pattern to appear similar to a pinwheel that made it difficult to see the ground between its pulses. However, their magnetron was only capable of 5 W of power, giving it very short range. They were so ineffective that they were abandoned in 1944. Another system, Roland, used a 50 W klystron, but it was also considered unsuccessful and abandoned around March 1945. Another klystron-based system, Postklystron, was designed by