Assuming that {HEAD ~ no tone signals} have been applied to {TAIL ~ the decoder} 14, the output signal from comparator 56 is at a low logic level 
applied to
Assuming that { HEAD ~ no tone signals } have been applied to { TAIL ~ the decoder } 14 , the output signal from comparator 56 is at a low logic level
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH