ECOTEST MKS-05 TERRA-P+ Operating Manual page 36

The value of the preset threshold level is fixed after all digits are programmed by
short pressing of the MODE button. To fix a new value of the threshold level, set all
digits on the LCD by pressing the MODE button, even if the values of the high-order
digits are not changed. Double extinction of the LCD will indicate that the
programmed level is fixed.
Press the THRESHOLD button and hold it pressed to check the value of the fixed
DER threshold level. The threshold level value will appear on the LCD in two
seconds.
When the THRESHOLD button is pressed for more than four seconds, the low-
order digit starts blinking, indicating that a new threshold level value can be
programmed. A two-tone audio signal indicates that the programmed DER threshold
level has been exceeded.
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