ECOTEST DKG-21 M Operating Manual page 74

(the user presses no buttons of the dosimeter), the
dosimeter will automatically return to the mode of DE
measurement indication. All changes made will be canceled.
Note. The DE threshold level value of 0.000 mSv is
set automatically after the dosimeter is produced
indicating that the alarm is switched off.
4.3.3.6 Setting the measure DE value to zero
Setting DE measured value to zero is performed in the
mode of DE measurement indication. To reset DE,
simultaneously press and hold MODE and THRESHOLD
until "CLr" symbols appear on the LCD of the dosimeter.
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