Dr. Friedrich Kirchstein of Siemens of Berlin developed the V-2 radio control for motor-cut-off (). For velocity measurement, Professor Wolman of Dresden created an alternative of his Doppler tracking system in 1940–41, which used a ground signal transponded by the A-4 to measure the velocity of the missile. By 9 February 1942, Peenemünde engineer Gerd deBeek had documented the radio interference area of a V-2 as around the "Firing Point", and the first successful A-4 flight on 3 October 1942, used radio control for "Brennschluss". Although Hitler commented on 22 September 1943 that "It is a great load off our minds that we have dispensed with the radio guiding-beam; now no opening remains for the British to interfere technically with the missile in flight", about 20% of the operational V-2 launches were beam-guided. The Operation Pinguin V-2 offensive began on 8 September 1944, when "Lehr- und Versuchsbatterie No. 444" () launched a single rocket guided by a radio beam directed at Paris. Wreckage of combat V-2s occasionally contained the transponder for velocity and fuel cutoff.