Cast Aluminum Enclosure. Metallic Hookswitch. Volume control handset. Noise-canceling microphone. 15" Armored Handset Cord. Extremely Vandal Resistant. Tamper resistant Hardware. Autodial: Programmed to automatically dial up to 31-digits when handset is taken off-hook. Extreme Operating Temperature Range -40°C (-40°F) to +60°C(+140°F). FCC & IC Certified, UL60950 Listed. Keylock Door