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