+There may be one or more InputValues for the same input of a filter which may be bound to conditions.
+Each InputValue will have its condition checked in the order of InputValues given in the configuration
+file. The first InputValue that returns true for its condition will be evaluated. Chaining a number
+of InputValues with conditions and an unconditioned InputValue works like the C language equivalent
+if( condition ) {
+ // compute value of first element
+} else if( condition2 ) {
+ // compute value of second element
+} else if( condition3 ) {
+ // compute value of third element
+} else {
+ // compute value of last element
+}
+
+Example: Set the gain to 3.0 if /autopilot/locks/heading equals dg-heading-hold or 2.0 otherwise.
+<digital-filter>
+ <gain>
+ <condition>
+ <equals>
+ <property>/autopilot/locks/heading</property>
+ <value>dg-heading-hold</value>
+ </equals>
+ </condition>
+ <value>3.0</value>
+ <gain>
+ <!-- Hint: omit a condition here as a fallthru else condition -->
+ </gain>
+ <value>2.0</value>
+ <gain>
+<digital-filter>
+
+If the element <abs> is used and set to the value "true", only the absolute value of the input
+(the positive part) is used for further computations. The abs function is applied after all
+other computations are completed.
+