The EXD sounder has been approved for use in potentially explosive atmospheres and very harsh environmental conditions. The unit incorporates a three stage alarm option with sixty three tones to choose from. These include four tones that can be recorded or customized by the installer. All tones can be pre-set during installation. The units also have the ability to be fitted with a telephone initiation function and can be used as the second ring output indicator for telephones when installed in very noisy environments. The design allows for termination inside the enclosure. The sounder is supplied with a mounting bracket as standard.