DF110S 110c Thermal Fuse 16A 250V
“Thermal fuse DF is an one shot device, after operating function have to be replaced.”
When inserted new 2x4GB modules in addition to the original 2x2GB modules to iMac mid 2011, it was only beeping on power off. Tried to swap all module placements around couple of times before they were all accepted. Now with 12GB total ram.