I was working the mid-shift (graveyard) this morning and about 4:30AM we started experiencing landline problems — Landlines are the communications we utilize to coordinate ATC instructions with surrounding facilities (like Oakland Center, Los Angeles Center, Salt Lake Approach, etc) — Apparently the airspace I was managing was not the only one experiencing problems as the problem involved multiple sectors. Additionally I was told several radio sites were down, meaning there would likely be “holes” where pilots would be unable to speak to ATC. As a precautionary measure, at approximately 6:45 AM Salt Lake Center was declared “ATC Zero,” meaning no additional traffic would be permitted to enter the airspace. Yes, this means at this moment all Salt Lake City departures are being held on the ground and no inbounds are being accepted. As of 7:05 (when I left work) nothing had changed. Wow, first time this has happened in Salt Lake Center’s history. Pretty historic, unfortunately.