An improved decoder 17, wherein said {TAIL ~ reference frequency} is in {HEAD ~ the range} of 250 Hz to 6 kHz 
An improved decoder 17 , wherein said { TAIL ~ reference frequency } is in { HEAD ~ the range } of 250 Hz to 6 kHz
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH