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 Configure Linksys SPA 3102 to send Fax with 3CX

IMPORTANT This guide has been tested with firmware version 5.1.10 (GW). Be aware that different firmware revisions may have different web interface formats and functionality.

  1. Follow the Steps described in the following administration guide:
    The Steps needed for this implementation are numbers 2 to 7 only. This will guide you in configuring the SPA3102 on your network and assigning it an IP address to make it accessible for configuration.
  2. Update the Linksys to the firmware 5.1.10(GW). Do not use a later version than this.

  3. Enable Line 1 to register the ATA with 3CX

    Click on the Line 1 Configuration tab.
    Under Network Settings configure the following:
    a) Network Jitter Level – Very High
    b) Jitter Buffer Adjustment – Disable

    Figure 1: Enable Line and configure Jitter settings for Fax sending

  4. Proxy, Registration settings and Subscriber Information.
    Note that you have to add an extension in the 3CX Phonesystem. In this example, extension 118 was added on the 3CX Phonesystem. 3CX resides on a machine with the IP address of

    Figure 2: Registration and Subscriber Information

  5. Supplementary Services

    Apply the following modifications:
    a) “Call Waiting Serv” : Set this to No
    b) “Three Way Call Serv” : Set this to No as well.

    Figure 3: Supplementary Services section

  6. Audio Configuration

    a) Set the PreferredCodec to G711u
    b) Set “Silence Suppression Enable” to No
    c) Make sure that the option FAX Enable T38 is set to Yes. (Default setting is Yes)
    d) “Echo Canc Enable” should be set to No
    e) Set the option “Fax Passthru Method” to REINVITES.

    Figure 4: Audio Setting Configuration In Line 1

  7. Connect the Fax Machine to the PHONE PORT in the Linksys SPA 3102. You should hear a dial tone as soon as you lift up the Fax Handset. Also the extension representing the ATA i.e. 118 should show as registered on the 3CX Phone System Line Status.

  8. Make some calls from a sip phone registered on 3CXto the ATA FAX extension and vice versa from the Fax machine (which is now a “SIP PHONE”) to the extension to make sure that you have both way audio and that functionality is as expected. If the call ends in a busy tone, please go to (signed on as admin and in advanced mode) voice -> line 1 and to the end of the page add to the Dial Plan “(xx.)” without the brackets. Repeat the test form point 8 to confirm both way audio.

  9. At this point you can proceed to test Fax sending functionality. Send a fax from the fax machine. Remember to insert the appropriate prefix if required.


If you will be using a VoIP provider to receive faxes via the Linksys 3102 (note that only a limited number of VoIP providers properly implement fax), then you need to do the following:

  1. Stop 3CX Fax Service and disable the service
  2. Set the Linksys 3102 ATA to register to the extension 888 (step 4) and fill in the password and authentication ID accordingly to the fax settings in the 3CX management console. Default password is 888
  3. Ensure that in the 3CX Management Console -> Settings -> Advanced -> “Custom Parameter” the entry “Fax direct SDP” is set to 1.
  4. Configure NAT settings: http://wiki.3cx.com/documentation/fax-1/receiving-faxes-from-voip-providers

Note: You will lose the ability to send Fax by Mail to the E-mail address of an extension. You must choose to either use the fax machine or the inbuilt fax server.

Article Details
Article ID: 709
Created On: Dec 22, 2009 07:01 PM

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