Solder-Type Head : A sprinkler head that operates when a fusible link is melted by heat, which allows the water-tight seal to be broken and water to discharge
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}