How can a Script be periodically invoked from the BGE? In a script I try to get the coordinates of a head tracker and to change the current scenes camera. The script is wired as shown in this image:



Unfortunatly the script is only called once. How can I setup the Sensor/Controller to invoke it periodically (preferably after a frame has been rendered)?
I had to click the small button (highlighted) and set the frequency to 1. 

The option is called bpy.types.Sensor.use_pulse_true_level