Telephone Extension 1
or
Status Code 1

1 by itself is ambiguous. ICUC thinks you might have entered an unknown telephone number shortcut abbreviation or a telephone number extension without a preceding telephone number or a status code without any telephone number to apply the status code to. To make use of telephone number shorthand abbreviations you must first perform a login from this device. After login, depending upon how you have set up your account, here are some valid ways to use a single .ac digit:

1.ac Ex: Access web site of recent telephone number who's last digit is 1
or
c.1.ac Ex: Calendar for last used telephone number ending in digit 1
or
e.1.ac Ex: Email last used telephone number ending in digit 1
or
i.1.ac Ex: Instant Message last used telephone number ending in digit 1
or
s.1.ac Ex: Get status of last used telephone number ending in digit 1
or
w.1.ac Ex: Access web site of recent telephone number who's last digit is 1
or
x.1.ac Ex: Access web site of recent telephone extension who's last digit is 1
or
800.555.1212.1.ac Ex: Access web site of telephone number 800.555.1212 extension 1
or
17.9797.800.555.1212.1.ac Ex: Set the status of telephone number 800.555.1212 x1 to status code 17 assuming that 9797 is a valid PIN code for performing status updates.

more information on telephone number shortcuts, extensions and status codes...