An adding unit adds {TAIL ~ the reference signal} to {HEAD ~ the filtered signal} to generate an output signal 
An adding unit adds { TAIL ~ the reference signal } to { HEAD ~ the filtered signal } to generate an output signal
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH