MaxBlast Single Trumpet Horn features a prewired, sealed sound unit. After a 600 hour salt spray test, this electric horn was completely rust-free! Horn wiring has no polarity, negative or positive can be attached to either wire. Mounting bracket can be used as a wiring template. When installed, the trumpet should point slightly downward to permit water drainage. At 118 decibels and a frequency (Hz) of 390±15A, this horn meets US Coast Guard’s COLREGS and ABYC standard A-23 for use on vessels under 12m (39′). Constructed with an over molded motor housing under a stamped 304 stainless steel exterior and diaphragm, which protects the internal components from corrosion. 5-year rust free warranty.