T.38 is a protocol for real-time transmission of fax over IP.

Kerio Operator uses T.38 by default. Ask your provider whether they support this protocol. If not, read section My provider does not support T.38.

Connecting a fax machine to Kerio Operator

1. Connect your fax machine to an Analog Telephone Adapter device (ATA — for example, Cisco SPA 112).

2. Assign one of Kerio Operator extensions to the ATA device.

The fax machine is connected to the network. You can send and receive faxes.

Configuring an ATA device

You can use various ATA devices. Each device has different settings. The following must be configured:

1. Enable T.38

2. Set fax passthru to ReInvite

3. (Optional) set FAX T38 Redundancy to 3, Echo Canc Enable to No, and Fax Tone Detect Mode to Callee Only.
   

   NOTE: Phone provisioning in Kerio Operator sets these variables automatically.

You can enable fax-to-email service for any extension. Kerio Operator then sends all incoming faxes to the user's email address as PDF attachments.

In the administration interface:

• Go to Users and enter an email address for each user.
  
  
• Go to Extensions and enable the Forward incoming faxes to user's address email address option for the particular user's extension.
  
  

Kerio Operator can send all incoming faxes to a single email address. For more information, please refer to the Receiving All Faxes to a Specific Email Address in Kerio Operator article.

If your SIP provider does not support T.38, you have to solve these issues:

• Enable codecs G.711 A-law/U-law for the transmission. High compression codecs would distort the signal.

• Reduce the speed on your fax machines (if supported).

Enabling G.711 A-law/U-law Codecs for the Interface

1. Log in to the administration interface.

2. Go to Configuration > Call Routing.

3. Click the provider's interface.

   

4. Click the Codecs tab.

5. Move G.711 A-law and G.711 U-law to the Selected codecs table.

6. Move G.711 A-law and G.711 U-law codecs up in the table. Click OK.

Fax messaging now uses codecs G.711 A-law/U-law.

Disabling the T.38 Support

Although your SIP provider supports the T.38 protocol, you may experience some difficulties in communication. The solution is to disable the support for the T.38 protocol:

1. In the administration interface, go to Configuration > Advanced Options.

2. On the Telephony tab, click Configure next to the SIP Configuration.

3. Uncheck the Use T.38 standard for faxing option.

   

4. Click Save.