ECOTEST DKG-21 Operating Manual page 46

Hold the THRESHOLD button down for more than 4 s to set the
threshold value to zero. The low-order digit will start blinking at that
indicating that a new threshold level value can be programmed.
A blinking red light-emitting diode and the ALARM transparency, as
well as a two-tone audio alarm indicate that the programmed DE threshold
level has been exceeded.
To inform the user that the DE threshold level is likely to be quickly
reached, the dosimeter sends an interrupted audio signal when 90 % of the
programmed threshold level is achieved. Press any button to switch this
audio alarm off.
Important! If the process of the new threshold level programming is
paused for more than 30 seconds (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.
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