| 摘要 |
In an exemplary embodiment, an mAs relay having selector keys and also a digitally operating manual control for selection of mAs products is capable of being switched over for digital selection of the exposure time independently of later radiographic current selection. For this purpose, the input of the mAs relay is capable of connection to an auxiliary current source which delivers a constant auxiliary current. The operating threshold of the mAs relay is then adjusted by the digital selection of exposure time. For the purpose of overload protection, a power circuit can be present which in a step-by-step fashion reduces the x-ray tube power via the x-ray tube current to a permissible value when preprogrammed times, e.g. planigraphic exposure times provided for planigraphic operation, are exceeded for the given settings of radiographic current and voltage.
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