| 摘要 |
In the device, actual-value and referene-value sensors (1,3,4) are provided to form at least two control differences, as well as at least two pumps (8,11), each feeding an additive into the liquid, the delivery rate of said pumps being adjustable by means of an adjusting member (14) controlled by the control difference, and at most one of which is in operation at any time. A common adjusting member (14) is provided for both pumps (8, 11) and can be connected to in each case one of the pumps (8, 11) via a changeover device (15). A comparator device (18) establishes the presence of at least one of the control differences and actuates the changeover device (15) as a function thereof. <IMAGE>
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