The high-voltage switches of the model series HTS-Sl and HTS-Fl have been especially designed for scientific and industrial power pulse appli?cations which require a fast and reproducible switching of peak currents at the kiloampere level. To achieve this, state-of-the-art power semicon?ductor devices, so-called IGBT's (lnsulated Gate Bipolar Transistors) have been employed. These new switching elements of power electronics represent in principal a combination of the classical bipolar transistor with the modern vertical MOSFET. The advantages of both technologies; the current capability and low voltage drop of the bipolar transistor plus the high switching speed of the MOSFET, are ideally combined in the IGBT. By using a hundred or more interconnected IGBT's the switching modules of series HTS-Sl/Fl achieve the pulse power capability of gas discharge tubes and spark gaps. Additionally, IGBT switches offer advantages like simple connection, short recovery time, low jitter and last but not least the lifetime typical of semiconductor devices.