diff --git a/KEITHLEY-2701/createImages b/KEITHLEY-2701/createImages
index 9ce525dbd21e206a850d2aad35baf58bb20bfc0d..58c471dc65296b4a413cbaf52bfdb088be35fea9 100755
--- a/KEITHLEY-2701/createImages
+++ b/KEITHLEY-2701/createImages
@@ -51,6 +51,7 @@ digitFile[7]='digit-7.png'
 digitFile[8]='digit-8.png'
 digitFile[9]='digit-9.png'
 digitFile[10]='minus.png'
+digitFile[11]=$emptyCanvas
 
 NUM2CHAR[0]='0'
 NUM2CHAR[1]='1'
@@ -63,6 +64,7 @@ NUM2CHAR[7]='7'
 NUM2CHAR[8]='8'
 NUM2CHAR[9]='9'
 NUM2CHAR[10]='-'
+NUM2CHAR[11]='_'
 
 digitPos[1]='+185+220'
 digitPos[2]='+207+220'
@@ -86,7 +88,7 @@ value=""
 DPR=$((RANDOM % $NUMBER_OF_DIGITS + 1)) # random dot position (1..$NUMBER_OF_DIGITS)
 for (( i=1; i<=$MAX_DIGITS; i++ )); do
   if (( $i <= $NUMBER_OF_DIGITS )); then
-    R=$((RANDOM % 11)) # random digit number (0..10='0'..'-')
+    R=$((RANDOM % 12)) # random digit number (0..11='0'..'_')
     eval DIGIT$i=${digitFile[R]}
     value+="${NUM2CHAR[R]}"
     if [ $DPR == $i ]; then