(Maitre'D 2003, from Service Pack 3 and later versions of Maitre'D)
If the system does not recognize a scanned bar code as a valid item, the
error message "ITEM NOT AVAILABLE" is displayed to notify the
user that the scanned item's bar code is invalid. A loud beeping sound
is also emitted and no other item can be scanned until the error message
is acknowledged by the user by touching OK.
