When {HEAD ~ a signal} indicative of {TAIL ~ abnormal condition} is outputted from the sensing means, a signal processing circuit is actuated 
indicative of
When { HEAD ~ a signal } indicative of { TAIL ~ abnormal condition } is outputted from the sensing means , a signal processing circuit is actuated
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH