another solution is to use used smart card phone card...
They usually have a unique serial number

On Wed, 2001-10-17 at 18:09, Alan B. Pearce wrote:
> >One other idea is to use mag swipe cards everyone has (fly buys, Medicare,
> >bank cards etc) you use track 3 which contains the card number and expiry
> >date, which is safe and non intrusive. commercial mag stripe readers are
> >available form inner range security products for about au$30 and it sends
> >the data out in a serial format.
>
> I guess you are looking for a real cheap solution so it does not matter if
> the cards do not come back.
>
> One scheme I have seen used was for room registration in a Youth Hostel,
> where your "card" was a heavy paper ticket printed with a bar code. There
> was a barcode reader associated with a block of about 4 or 5 doors, and
> inserting the card released a security door style magnetic lock. The barcode
> was associated with an expiry time in the computer booking system, so you
> were automatically "booked out" when it expired.
>
> The disadvantage is that all the doors and readers need wiring back to some
> central computing system, but I suspect you were looking at that anyway if
> looking into smart cards.
>
> --
> http://www.piclist.com#nomail Going offline? Don't AutoReply us!
> email listserv@mitvma.mit.edu with SET PICList DIGEST in the body
>

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listserv@mitvma.mit.edu with SET PICList DIGEST in the body