The present invention relates to a mobile communication terminal for Push To Talk and a method for processing missed call information thereof, which allows a receiver to check why an originator requested the PTT telephone call during the absence of the receiver through missed call information. One or more acoustic transducers are carried in a distal portion of the acoustic lead and configured for converting energy between electrical energy and acoustic energy, wherein electronics for driving the one or more transducers are carried in the housing. 5\u03bbp, wherein \u03bbp is the spatial variation length of the electric field intensity in the microstructured region. Other embodiments are described and claimed. The fluorescent layers are ordered in the form of a stack for providing a flat-field calibration standard over multiple bands of wavelengths.