When {HEAD ~ the temperature} is within {TAIL ~ a normal operating range} in which unburned particulates accumulate on the duct, the digital pulses are accumulated in a first counter, the value of which count corresponds to the duration of time that the sensed temperature remains within the normal operating range 
is within
When { HEAD ~ the temperature } is within { TAIL ~ a normal operating range } in which unburned particulates accumulate on the duct , the digital pulses are accumulated in a first counter , the value of which count corresponds to the duration of time that the sensed temperature remains within the normal operating range
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH