User interface 520 may include mechanisms for inputting information to {TAIL ~ user device} 210 and for outputting information from {HEAD ~ user device} 210 
User interface 520 may include mechanisms for inputting information to { TAIL ~ user device } 210 and for outputting information from { HEAD ~ user device } 210
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH