When a valid key is presented to the dispenser the display will alternately
flash the key totals then the key number, until the nozzle is lifted. The key
number is displayed as "c xx" where xx is the keynumber. The access
number is never displayed.
If an invalid key with the correct access code is presented to the dispenser
the display will show "----" for one second then the key number for one
second.
If a key with an incorrect access code is presented to the dispenser then
the display will only show "----" for two seconds.