A key word in the command from the officer in charge at a fire directing fire alarm operators to sound a specific signal calling for more equipment, as "strike a second alarm;" it probably comes from the tower alarm bells that were originally struck
Ralph W. Burklin & Robert G. Purington, Fire Terms: A Guide to Their Meaning and Use, National Protection Association, Boston, MA 1980 USA. (Guide: Meaning and Use, Nat Prot Association Fr Srvc - Amer) {457}