correct some headline level mess
Input Values ====
The direct inputs of controller and filter elements support so called input value lists. This is useful, if the input should be connected to one of many separate inputs like autopilots connected to NAV1, NAV2 or the GPS. The well known <tt><condition></tt> element is allowed within an input value element. The input value list will be traversed until the first input value with a successful condition is found. The behavior is much like the switch statement in programming languages.
== filter ==
The [http://en.wikipedia.org/wiki/PID_controller PID controller] is the swiss army knife of automation and this implementation is suitable for most situations. It has a builtin anti-windup logic, and usage of <max> and <min> elements for calmping the output is mandatory. The most important thing to know is that this controller 'does not' compute absolute output values but an offset from the current value of the output property. This can lead to unexpected behavior if the current value of the output property is unknown when the controller is enabled. This behavior is different to that of the pi-simple-controller.
The xml element creating a pid controller is <tt><pid-controller></tt>.
This controller implements a PI controller. Other than the PID controller, it computes absolute output values, regardless of the value of the output property. It can by configured as an I-only, P-only or PI-controller. It has anti windup logic if <min> and <max> elements are present.
The xml element creating a PI controller is <tt><pi-simple-controller></tt>
: gain of the integrator component