The IS piezo alarm type ALT3 is an intrinsically safe sounder that may be used in group I hazardous areas such as underground coalmines. The alarm may be used as a pre-start alarm or as a general-purpose audible alarm. The sounder has a wide operating voltage range from 2.0 volts to 18.36 volts and consumes a maximum of only 10mA making it ideal for use on long conveyors where voltage drop can be an issue. The ALT3 easily mounts in a 28.6mm diameter hole within the host enclosure and provides an ingress protection level of IP55. The high sound pressure level of the sounder 85dBA further increases the utility of the sounder in noisy underground coal mining applications. The single-hole mounting and convenient flying lead termination provides for easy installation of the piezo alarm within the host enclosure. The low profile and small size of the piezo alarm on the outside of the host enclosure ensures minimum damage from any impact by external objects. The wide operating ambient temperature range of -20ºC to +40ºC further increases the utility of the piezo alarm type ALT3.