A hands free telephone set has {HEAD ~ both transmit and receive channels} open for {TAIL ~ the reception} of signals, while still inhibiting feedback singing 
open for
A hands free telephone set has { HEAD ~ both transmit and receive channels } open for { TAIL ~ the reception } of signals , while still inhibiting feedback singing
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH