Back-up alarm, 12 - 24 volt, Adjusts automatically to environmental noise reducing the sound level from 112 to 87 dB(A). 60 pulses per minute. Polarity protected solid state epoxy-potted electronics. Steam-cleanable. Two position fixing bracket. EEC and CE approved. N.B. This alarm MUST HEAR the surrounding noise level to adjust its output. Mount alarm at rear of vehicle facing the back, without obstruction.