a second amplifier configured for amplifying the data received from {TAIL ~ the second I/O port} and outputting the amplified data to {HEAD ~ the first I/O port} 
a second amplifier configured for amplifying the data received from { TAIL ~ the second I / O port } and outputting the amplified data to { HEAD ~ the first I / O port }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD