System Sensor 5602 194&deg;F Fixed Temp/Rate-of-Rise, Single-Circuit Mechanical Heat Detector Multiple configurations for installations:  Single- and dual-circuit models  Fixed temp and combination fixed- temp/rate-of-rise 135F or 194F ratings. Easy-to-use terminal screws A broad range of back box mounting options:  Single gang  3.5? and 4? Octagonal  4? square with square to round plaster ring Reversible mounting bracket The reversible mounting bracket permits both flush- and surface-mount back box installations.