On Tue, 01 May 2007 18:24:50 +0100, James Farrar
wrote:
On Tue, 1 May 2007 15:05:40 +0100, Tom Anderson
wrote:
On Mon, 30 Apr 2007, wrote:
On 23 Apr, 20:47, Paul Corfield wrote:
On Mon, 23 Apr 2007 20:09:41 +0100, Tom Anderson
wrote:
Also, am i right in thinking paper tickets either don't have a unique
ID on them, or that this isn't recorded by gates? If not, LU should
already have had this data.
Some magnetic tickets did have unique numbers but they were a very
small part of the overall population. The vast majority did not and
although they were counted by type at each gate you could not follow
"ticket 123456" through the system.
Presumably there is some way to identify a ticket within a station - so
that things like gate zig-zag can be identified?
A way to do that would be for the gate to write on the ticket that it's
just been used for exit at that station, and refuse tickets that have been
so marked. This is probably actually simpler, as it avoids having to have
the gates share knowledge of which tickets they've seen.
I believe magnetic tickets hold the details of the last three uses.
No they do not. They do not have sufficient capacity to do so. If a
ticket is valid and is accepted then certain key fields are updated. It
is this revised data that allows things like passback and zig zag to be
detected. Invalid tickets are not rewritten when put through a gate so
as to preserve the aspects of the ticket that are invalid.
--
Paul C
Admits to working for London Underground!