On Sat, 12 Nov 2005 01:14 +0000 (GMT Standard Time),
(Colin Rosenstiel) wrote:

In article ,
(Paul Corfield) wrote:

On Wed, 09 Nov 2005 22:51:04 GMT, "Richard J."
wrote:

Colin Rosenstiel wrote:

My Cambridge to Underground Zones 1 & 2 tickets don't get eaten at
East Putney which is much more baffling.

Only because you've forgotten the answer! This was covered in a
thread you initiated here in January 2003, which included these two
explanations:

From Clive Feather, 7 Jan 2003:
"The magnetic code contains a common portion, an LU portion, and a
National Rail porton. To a first approximation, LU gates don't
understand the NR bit of the ticket and vice versa; they'll simply
note that both parts are marked active and play safe, giving you the
ticket back."

From Paul Corfield, 6 Jan 2003:
"Any ticket with any National Rail validity will always be given
back. The gate cannot know if you have used the NR validity or even
if it is "beyond" the exit point of the gate itself - e.g. you used
the NR bit between Cambridge and London but the ticket isn't reset to
reflect this. You then enter the LUL system and record an entry. The
gate at East Putney says "has this ticket got the right validity from
where it entered (LUL) to where I am? Oh yes that's OK. Oh look this
has some NR validity - don't know where but I'd better give the
ticket back in case that's the next bit of the journey". "

http://groups.google.co.uk/group/uk....owse_frm/threa
d/41a7659a88aadfe9/

Which I have, in effect, just repeated. And we get another negative
response and then a demand for another explanation for something that
no one on this group is accountable for. I give up.

That NR and LUL validity are handled separately I can understand but not
realising where the ticket is actually valid to is harder to cope with.
If it's a ticket to an LUL destination surely it's not that hard to work
out it's done it job on exiting at LUL?

The LU gate does NOT read the NR bit. It just knows from the ticket type
that it has some validity on NR somewhere. That may or may have been
used, it may or may not start at the station where you exit LU or you
may need to walk down the street to a NR Station as at East Putney /
Putney. As the gate cannot know if you still need to use the NR portion
it has to default to giving you the ticket back. It reads the LU bit
which on your ticket would be a trip in Z12. The gate will read an entry
point into LU within those zones and then check to see if where you are
exiting is also in Z12. If it is then the LU bit is used up, the gate
opens, gives you your ticket back and off you go.
--
Paul C


Admits to working for London Underground!