Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 6.5
Communication Breakdown; Other / Unknown; Situational Awareness; Time Pressure
ATC Issue All Types; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued New Clearance
Human Factors
I relieved the previous Controller and started working traffic. I was told that it was hard to communicate with Aircraft X because of his low altitude and the BUEC [Back up radio] was OTS. When I sat down Aircraft X was non-radar.  I saw the code for Aircraft X and tagged the data block up with the aircraft. A fter identification the MSAW flashed and I realized that the aircraft was in a 6;500 feet MIA box level at 6;000 feet MSL.  I immediately climbed the aircraft to 7;000 feet MSL for the remainder of his flight.Recommendation: We have been trained to check the MIA.  It was a mistake and no recommendations needed.
ZLC ARTCC Controller reported realizing an aircraft was at the wrong altitude for his sector an initiated an immediate climb.