ECOTEST DKG-21 Operating Manual page 47

4.3.3.7 Setting the measure DE value to zero
Setting DE measured value to zero is performed in the mode of DE
measurement indication. To reset the DE, simultaneously press and hold
MODE and THRESHOLD buttons until "CLr" symbols appear on the
dLCD of the dosimeter. As soon as "CLr" symbols are displayed, release
the MODE and THRESHOLD buttons.
Shortly press the MODE button to confirm DE reset. The "CLr"
symbols will blink three times and the dosimeter will return to the mode of
DE measurement indication as a confirmation of reset. To cancel reset,
press shortly the THRESHOLD button, or do not press the buttons for 30
seconds (in this case, the dosimeter will automatically return to the mode
of DE measurement indication).
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