A system for exchanging {HEAD ~ data} between {TAIL ~ a portable payment terminal} and a stationary base terminal in communication with a payment center 
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A system for exchanging { HEAD ~ data } between { TAIL ~ a portable payment terminal } and a stationary base terminal in communication with a payment center
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH