A Distress Signal Unit will sound a high pitch alert if activated (this can be either manual or if no movement is detected within a period of time) this alert will cause other firefighters to become aware that a fellow colleague and friend is in trouble and requires urgent assistance. Whilst the current system is tried and tested, I believe it can be improved by addition of beacons, ultrasonic sensors and bluetooth to allow firefighters to know where one and other are and assist with object detection/avoidance.