The sounders from the DS series are designed for the requirements of industrial conditions and can be used as universal alarms. The sounders which are suitable for use both indoors and outdoors, generate warning signals in 31 different tones that can be selected with the aid of an internal switch. Pressure chamber-sound system: Outstanding penetration of audible obstacles like walls and doors, high proportion of low frequencies. Therefore, a smaller number of sounders is needed. They are particularly suitable for fire alerting, as they are VdS and EN 54-3 certified. Aluminium housing with high IP protection (IP 66/67): Wide application range (dust and fog). Secure use in the outdoor area with highest reliability. Further operating temperature range: -40 to 55 deg C Dimensions 143 x 133.5 x 133.5 mm These devices are very sturdy, robust and durable, therefore they come with a 10-year warranty. Sounder variations and options.