Access control system

An access control system for a public transport system having a plurality of entrance/exit locations the control system comprising, at each entrance/exit location, at least one entrance gate which is provided with a ticket reading facility, at least one exit gate which is provided with a ticket reading facility, a local data processor, a data communication channel between the or each entrance gate and the local data processor, and a data communication channel between the or each exit gate and the local data processor, the control system further comprising both a data communication network interconnecting the local data processors and at least one ticket issuing facility for issuing single-fare tickets which carry respective identification codes,

• characterized in that the or each ticket issuing facility is connected to the data communication network.
• In that each ticket issuing facility is arranged to communicate, upon issue thereby of a single-fare ticket, the identification code of that ticket and the location(s) for which the ticket is valid for opening an entrance gate, to the local data processor which is situated at the or each such location, and each such local data processor is arranged to respond by recording that a ticket bearing this identification code is valid for opening an entrance gate at the corresponding location,
• in that each entrance gate is arranged to communicate, upon presentation of a single-fare ticket to the ticket reading facility of that gate, the identification code of that ticket to the local data processor at the corresponding location and the local data processor is arranged to respond, if and only if it has a record that a ticket bearing this identification code is valid for opening an entrance gate at the corresponding location, by (i) permitting opening of the corresponding entrance gate and (ii) cancelling its record that a ticket bearing this identification code is valid for opening an entrance gate at the corresponding location,
• in that each local data processor is arranged to communicate, upon opening of an entrance gate at the corresponding location in response to the presentation of a single-fare ticket to the ticket reading facility of that gate, the identification code of that ticket to the local data processor at the or each location at which that ticket is valid to permit exit from the system and the or each local data processor to which this code is thus communicated is arranged to respond by recording that a ticket bearing this identification code is valid for opening an exit gate at the corresponding location,
• in that each exit gate is arranged to communicate, upon presentation of a single-fare ticket to the ticket reading facility of that gate, the identification code of that ticket to the local data processor at the corresponding location and the local data processor is arranged to respond, if and only if it has a record that a ticket bearing this identification code is valid for opening an exit gate at the corresponding location, by (i) permitting opening of the corresponding exit gate and (ii) cancelling its record that a ticket bearing this identification code is valid for opening an exit gate at the corresponding location,
• and in that each local data processor is arranged to communicate, upon opening of an exit gate at the corresponding location in response to the presentation of a single-fare ticket to the ticket reading facility of that gate, the identification code of that ticket to the local data processor at any other location at which that ticket was valid to permit exit from the system and the or each local data processor to which this code is thus communicated is arranged to respond by cancelling its record that a ticket bearing this identification code is valid for opening an exit gate at the corresponding location.