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Looking for FAXStation info?

This wiki is for fax services that use our SIPStation unlimited two-way trunks. For information on our new fax trunk services (FAXStation), please see the FAXStation wiki.

How does it work?

We have implemented a reliable outbound fax service that we believe provides the most reliable fax service in the VoIP industry. We assure end-to-end T.38 delivery to our PRI-connected fax server to ensure your faxes hit the PSTN without improper transcoding and conversions. Our SIPStation fax service is available for the lower 48 US only and is delivered as a metered service at a per-minute rate. Inbound T.38 calls are part of your normal trunking service and do not carry a per-minute charge. Please visit to view the SIPStation terms of service.

In order to gain access to the fax service, you need to be set up for the "metered services" option in SIPStation. Metered services deduct funds from your reserve account as described in our wiki "How Metered Service Works."

How do I sign up?

  1. Log in to the SIPStation Store at

  2. Click on the "My Account" tab in the menu at the top of the page.

  3. Scroll down toward the bottom "Metered Services" section.

  4. Enable T38 Faxing by changing the On/Off switch to "On" (green).


Outbound T38 faxing in SIPStation is a pre-paid, metered service. When you enable T38 faxing, "Top Up Settings" are also automatically enabled as shown above, and your account will be charged the Top Up Amount. This amount will be placed in your reserve account, and the per-minute fax charges will be withdrawn from that balance. You can click the "Update" button if you need to change the default amounts. For more information on Top Up Settings please view our wiki "How Metered Services Work."

Once signed up, how do I make outbound T.38 fax calls?

All outbound T.38 fax calls need to be sent to us using a prefix of *323 and then either a 10-digit or 11-digit number. For example, if you wanted to send a fax to someone at 5555551234, you would send the call to SIPStation as *3235555551234.


If we do not receive *323 at the beginning of your number, outbound faxing will not work. In FreePBX, you will need to configure an outbound route accordingly. Unless users are faxing from the User Control Panel with a global fax prefix set up, they will need to dial *323 or a special prefix you have set up for faxing.

Configuring an Outbound Route for Fax

You will need to set up an outbound route that uses dial patterns involving *323 plus a 10- or 11-digit number. There are generally two ways you could set this up.

Example 1: The first option is to create dial patterns where a user must dial *323 followed by a 10- or 11- digit number. The advantage is that this somewhat simplifies things; the disadvantage is that users now need to remember to dial *323 before a fax number, and that may be difficult to remember.

Example 2: The second option would be to set up a special "simplified" prefix for users to dial. For example, you could allow your users to dial 9 plus any 10- or 11-digit number to send a fax as shown below. Your dial patterns would strip the 9 and prepend *323 to the beginning of the number. Users would not have to dial *323. (You can choose any prefix you would like. If you choose something like "9," the advantage is that users can more easily remember a single-digit number than the actual fax prefix of *323.)

Outbound Route Order

Don't forget to drag your Fax outbound route toward the top of your route list. It should be below any Emergency routes but above other types.

Global Fax Prefix

If using Fax Pro in FreePBX to send outbound faxes from the User Control Panel (UCP), UCP can automatically add a fax prefix. The advantage of this is that UCP users would not have to remember any prefix when faxing from UCP. Instead they would just need to dial a 10- or 11-digit number. UCP would add the global prefix to the beginning of whatever the user dials. When setting this up, you just need to keep in mind that the resulting combination needs to match something in an outbound route for fax. Also keep in mind we need to receive *323 at the beginning of a 10- or 11- digit number in order for outbound faxing to work in SIPStation.

To set this up in FreePBX, go to Settings → Fax Configuration and look for "User Control Panel Faxing Options."

The global prefix you need to use will depend on what you've set up in your outbound route dial patterns. There are generally two ways you could set this up.

Example 1: If your dial patterns are *323NXXNXXXXXX and *3231NXXNXXXXXX (no prefixes or prepends), then your global prefix needs to be *323.

Example 2: If you have set up a "simplified" fax prefix as described earlier, then your global prefix needs to be whatever special prefix you have set up in the outbound route For example, if you want users to dial 9 when faxing, and you've set up a dial pattern that strips the 9 and prepends *323, then your global prefix would need to be 9.

Remember, if you set up a global prefix, users should not dial any prefix when faxing from UCP. They simply need to enter the fax number.

Enabling T.38 in Asterisk

T.38 & Asterisk

Please note, in order to use SIPStation faxing, you must have Asterisk set up to handle T.38 at the Asterisk level. We are not able to offer technical support for this. FreePBX does have an option to enable T.38 in the Asterisk SIP Settings module, but you also need to make sure Asterisk is compiled for T.38.

In FreePBX, go to Settings → Asterisk SIP Settings → Chan SIP (right-hand side). Scroll down to Audio Codecs and make sure T38 Pass-Through is enabled.

Configuring Fax Settings in PBX Modules

For fax configuration instructions, please visit the appropriate wiki below: