Which FXS ATA (VoIP gateway) to use?

  • Marco Paland

    Marco Paland - 2013-02-27

    Perhaps anybody here has the same problem: Connecting old analog phones to raspbx.
    Which reliable FXS ATA (4 FXS ports needed) do you use? USB or network attached?

    Unfortunately there's (not yet) no "PBX" piggyback-board for raspberry which provides 2/4 FXS, FXO and a BRI port as single-system solution... :-(

  • Gernot

    Gernot - 2013-02-27

    I always recommend AVM FritzBox, but AVM is a bit Europe-centric, maybe not so well available in other parts of the world.
    The older model 7240 can be found quite cheap on Ebay, has 2 FXS ports and DECT capability. You can directly register DECT phones on it.
    Not 4 ports as you wished, but maybe you want to use DECT anyway?

  • Michel

    Michel - 2013-04-03


    This post may perhaps help some Raspbx users that have to deal with some older PSTN devices connected to ATA FXS ports in auto answer mode (like a fax machine).

    I put one of these devices (remote control system) behind a Grandstream 488HT ATA (american brand) registered to Raspbx.

    When trying to call this remote control unit through the Grandstream ATA, I got no response.
    If replacing it with an old telephone on the same ATA FXS port, the phone was ringing correctly when inbound calls occured.

    By default american ATA's send ringing bursts which frequency is 20 Hz. In european countries (I live in Belgium), this frequency is approx. 25 Hz (this frequency is specific to country technical regulation. It is set up to 50 Hz in France for example).

    ETSI (European Telecommunications Standards Institute) recommandation is:

    To ensure reliable detection by all terminals, a ringing signal frequency of 25 Hz ± 8 % is recommended for ringing generators, and for terminal equipment it is recommended to detect ringing signals of 25 Hz ± 10 %.

    This frequency shift (25 Hz --> 20 Hz) may be critical for some european terminals behind american ATA's. That was the case with my remote control.

    Unhappily, the Grandstream HT488 ringing frequency (generated out of the FXS port) couldn't be modified.

    After some search, I found that Linksys Cisco SPA 112 enables frequency settings. Factory default is 20 Hz but may be set to 25Hz in SPA 112 Voice Parameters.

    Buying this ATA and setting frequency to 25 Hz solved my problem as I could again reach my remote control device.

    "Europe-centric" device may best suit european regulation if you are located in Europe but brands from other countries may also be used if configurable and if configured correctly.

    Following links from ETSI (European Telecommunications Standards Institute) provide more information about these technical regulations:




    PS: probably other brands, as well as Grandstream other ATA's, have same frequency configuration possibilities but my Google search mentionned Linksys Cisco SPA 112 first. It is also supposed that such devices (remote control) sold in North America work flawless behind a Grandstream ATA.
    As previously mentionned, problems I encountered might also appear with older PSTN equipment sold in Europe. I recently bought a new fax machine in Belgium that works correctly behind my Grandstream HT488 ATA.

    Last edit: Michel 2013-04-07
  • jim

    jim - 2013-05-08

    Patton 4114
    Grandstream gx4004
    All work well with asterisk for 4 port fxs
    If you need more fxs look at dinstar gateways
    Linksys spa400 good 4 fxo port gateway but old now
    Cisco 8800 best of both with 4 fxs and 4 fxo but expensive

    Last edit: jim 2013-05-08
  • VoIPuser

    VoIPuser - 2013-07-29

    I'm surprised that no one's mentioned the Obihai devices in this thread. As long as you aren't trying to support an old pulse-dialing (rotary dial) phone, the Obihai devices are truly the best available at the present time. The OBi200 is their latest single line model, while the OBi202 is their two line model. Unfortunately, they don't currently make anything that supports more than two lines. I don't know what four-port devices sell for, but you might find that two OBi202's would be less expensive and give you better results.

    It's just worth mentioning, for the benefit of anyone else that might happen across this thread, that there are also a couple of older Obihai models: The OBi100 single line model, and the OBi110 which has one FXS port and one FXO port. You can still find these on sale occasionally at Amazon and other sellers, but I expect that when the current supply is gone, only the newer models will be sold. In the case of the OBi110, there is no newer direct replacement, but you can use either the OBi200 or the OBi202 with one OBiLINE device (basically an FXO port that plugs into the USB connector on either an OBi200 or OBi202).

  • Bill

    Bill - 2013-08-20

    if your on a budget I have had good luck with the grandstream series of gateways.
    if you have a bigger budget, the audiocodes line of gateways works well,they are a pia to configure but I have several running now in production.

  • advocate

    advocate - 2016-01-10

    I second the suggestion of Obi 200 and their other devices. Obi devices have the very best sound quality and I've even found that they handle fax machines over uLaw without any issues. If you just need one or two, you cannot go wrong with the Obi 200 or 202. I believe that they also have 4 line devices, but I haven't investigated them.

  • atux

    atux - 2016-04-14

    i am using 3 fritzbox 7170 with 3 fxs each one, 9 fxs in total and 3 BRIs. you can find them under 50€ each on ebay. for me it is the best solution and i have it working for almost 5 years without any issues.
    the only change was to dump the PC running asterisk and replace it with raspberry. the rest of the hardware is still the same.

  • carriba

    carriba - 2016-12-17

    You may also try the Planet VGW-402, a 4-port SIP VoIP Gateway that has 2 FXO ports and supports Caller ID and other PSTN features.

    Other models with more analogue ports for FXS and FXO interfacing are also available.


Log in to post a comment.

Get latest updates about Open Source Projects, Conferences and News.

Sign up for the SourceForge newsletter:

No, thanks