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).