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To set the criterion level to 80 dB and the exchange rate to 3 dB, set the next 4 positions down.
For a high threshold of 80 and a low threshold of 70 set the first 4 positions of the right switch to
down, up, up, and up.
To identify this unit as unit 0 set the next three switches down. (If the unit number is set to zero
the code will not show the leading zero.)
All the switch positions in a column must be set to get the correct settings. Notice, as an example,
the 115 dB upper limit switch could be up or down depending on the range setting. Also the threshold
settings are encoded.
The M-27 reads the switches 1 and 2 only when the unit is reset or a battery is reconnected. If the switch
positions are changed when the unit is operating, the change will be ignored. Switch 3 is read at the start of
a printout. It may be changed to allow printouts to different printers or computers without destroying the
accumulated data.
Code Decoding
The M-27 displays two different codes; a 4-digit code can be decoded to show the position of 13
switch positions, and a 3-digit code shows the position of 11 switch positions.
For the 4-digit code:
1. Press CODE/HL3 until a 4-digit code appears.
2. Enter the code in the table.
3. Convert from hex to binary (see Table 1).
4. Subtract 1 from first digit (2 becomes 1 and 1 becomes 0).
5. Look up each position as described under Setting Internal
Switches.
1 decodes to a 12-hour clock.
0 decodes to "A" weighting, 50 dB range, 115 dB U.L. and Slow time constant.
The first E decodes to a 90 dB Criterion Level and a 5 dB exchange rate.
The last E decodes to a 90 and 80 dB thresholds.