Embodiments of a passive infrared detector can distinguish between an intruder and a small animal passing nearby the detector with a high degree of accuracy without substantially detracting from the ability to detect the intruder within a coverage area farther from the detector. The techniques can be implemented to use a new Java Bytecode instruction which is suitable for execution by a Java virtual machine. The control system controls the trajectory of the projectile system, for example by activating the transverse propulsion system to adjust the trajectory. The fixed frequency processor wirelessly receives safety-related train running information at a predetermined fixed frequency. The modified color bursts are defeated, in other versions, by modifying the horizontal sync pulse signals immediately preceding the modified color bursts so that the modified color bursts are not detected by a VCR and hence have no effect.