jimb@athertn.Atherton.COM (Jim Burke) (07/21/89)
A reader sent me mail regarding a previous posting I made about a
gas station using magnetic striped cards to operate their pumps.
Sorry, I deleted the mail and lost his name, but he made a very
interesting observation that I had overlooked. I had assumed that
the stripe unit in the store wrote to the card and the gas pump
read the card and then deducted an amount from the card, rewriting
the new amount back to the card. The reader suggested that each of
the cards might have only a serial number encoded on it. The store
unit simply reads the serial number and credits the account with
some dollar amount on a remote computer. The pump then reads the
serial number from the card and then communicates with the remote
computer regarding status and updates to the account. Nothing
ever gets written to the card itself. I don't know what scheme
this system actually uses but this makes a great deal more sense
that using the card media to store all the transaction data. Thanks
to the reader who mailed to me, I'm sorry for forgetting your name
or I would credit you with unravelling the mystery...
--
Jim Burke (408) 734-9822 (temp) | I'll stop posting when they pry my
jimb@Atherton.COM | cold, dead fingers from the smoking
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