lowering the power level applied to the heating means to the next lower power level upon detecting a rate of change exceeding {HEAD ~ the reference rate} and raising the power level applied to the heating means to the next higher power level upon subsequent detection of a rate of change less than {TAIL ~ the reference rate} 
lowering the power level applied to the heating means to the next lower power level upon detecting a rate of change exceeding { HEAD ~ the reference rate } and raising the power level applied to the heating means to the next higher power level upon subsequent detection of a rate of change less than { TAIL ~ the reference rate }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL