[en] This report describes the commissioning of the 350 Kv Pantak HF 420 C X-ray set to be used for the calibration of radiological protection instruments and to determine their response as a function of energy. The work presented in this report was carried out in the Dosimetry Laboratory of the Berkley Nuclear Laboratories (BNL), Central Generating Electricity Board (CGEB), Bristol, England, during the fellowship period 31st March to 2nd July 1983. (author)