The ledger may be kept at {TAIL ~ a central control system}, at a local network for localized transaction tracking, or at a remote network for {HEAD ~ more regional or national transaction tracking} 
The ledger may be kept at { TAIL ~ a central control system } , at a local network for localized transaction tracking , or at a remote network for { HEAD ~ more regional or national transaction tracking }
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD