Several months ago, we did a Quick Tip that explained how to use OS X’s built-in fax ability to set up a network fax server. Response to this tip was excellent. Many people wrote back asking if there was a way to enable Distinctive Ring on the Fax Server.

Distinctive Ring is a service that many phone companies offer. It allows two phone numbers to ring through on the same telephone line. This allows you to keep your normal phone number for phone service and add an additional number to the same line that is strictly for another use, such as fax service. If you subscribe to the service, your phone will ring with a separate ring tone when the fax number is dialed. Your fax would then need to know to answer that unique ring tone. This is what we need to teach OS X to do.

When I wrote the original tip, there was no documented way to enable Distinctive Ring for the fax server. Since that time, MacWorld published a tip in their monthly magazine, and MacOSXHints.com also published a way to manually enable the feature.

If you are experienced with the Terminal, just follow these steps. Please keep in mind that a mistake here could leave your computer unable to fax at all.

I have been informed that this modification does not work with every modem that Apple has shipped. I have not found a compatibility list, so you have to try it for yourself. The steps that follow, detail how to make a backup of your config file prior to updating it, as well as how to restore it should you have problems after the mod.

This mod assumes that you are comfortable with OS X’s command line, and are familiar with commands like cp and pico.

First, backup the fax config file:
# sudo cp /usr/bin/fax /usr/bin/fax.bak

Next, open the fax config file to make the modification:
# sudo pico /usr/bin/fax

you will likely be prompted for your admin password.

Find this line:
INIT="-iZ -i&FE0&D2S7=120 -i&C0"

Modify that line to read exactly as follows:
INIT="-iZ -i&FE0&D2S7=120 -i&C0-SDR=2"

That’s it. Now just exit pico by typing Control-x. Hit the y key, and then return to save the modified file. Now would be a good time to reboot.

If you have problems after running the modification, restoring the original file is easy. Just run this command:
# sudo cp /usr/bin/fax.bak /usr/bin/fax

If the terminal prompts you asking if you want to overwrite the existing file, just type the letter y and hit return. Reboot, and you are back where you started!