Suitable for Subzero Environments. 40°C (-40°F) to +60°C (+140°F). North American Listed for All Hazardous Groups. cUL / UL Listed. Replaces Explosionproof Telephones w/o Replacing System Cable in Most Applications. Braille Metallic Keypad. "Shrill”-Type Penetrating Ringer. Noise-Cancelling Microphone. Volume control handset. Low Sidetone for Noisy Environments. Switchable Power Supply - 110VAC/220VAC. Hytrel® Coil Cord for Maximum Durability. Hearing Aid Compatible (HAC).