Apple Express Fax/Modem - Manual (Page 54)

3 To charge a fax to your credit card account, click the Telephone Credit Card checkbox,
then enter your credit card number.
Many phone systems send a tone to indicate when the calling card number
and PIN should be entered.
4 To continue setting up your fax, click OK.
Fax Sender protects your privacy by hiding your credit card number when the
Options dialog box is reopened.
42 C H A P T E R F O U R
To detect the tone, enter a colon (:) in front of the
credit card number. If you find that the tone is not
being properly detected, enter one or more commas
to pause before sending the calling card number.