A Still Alarm is the basic structure fire response protocol of the Chicago Fire Department. The term "Still Alarm" came about upon the advent of telephones becoming more prevalent in reporting emergencies. The alarm office's register that received the signals from the actual fireboxes would remain "still" when someone reported a fire or emergency via telephone. The Still & Box is either transmitted by companies upon arrival at the scene when needed or due to multiple reports or confirmation of a fire. If there is a confirmed fire, the Still & Box Assignment may be added to the "Still" or "High-Rise Still" assignment upon request of the ranking officer on the scene. The Rapid Intervention Team (R.I.T.) Response is sent when the "Still" becomes a working fire, or upon request. The Mayday Assignment is used when firefighters operating on the scene of any emergency become lost, trapped or are discovered to be missing. Any member of the Chicago Fire Department of any rank or title operating on the scene of an emergency is authorized to call for a mayday response if they so feel the need. Some Units will act as Rapid Intervention Team deployment units and some units will act as "Still" Units on most Fire incidents.