In a communication device comprising a message function a certain short message or other reply message is sent in response to an incoming call in a situation where the user can’t answer the call himherself. By way of example, the mask or reticle is inspected, exposed to radiation at a specified wavelength, and then reinspected. The disclosed embodiments eliminate the need for automatic target acquisitionrecognition algorithms necessary for purely passive target tracking. The method is characterized in that a chosen electrical energy is applied to the sensor head resulting in a change in the optical signal being received by the optical interrogation device, and calculating a calibration signal, e.