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Interfacing to third-party analog party-line intercom systems

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  • Interfacing to third-party analog party-line intercom systems

    Interfacing to an existing third-party intercom system can be a tricky undertaking. First, you'll need to have purchased a Unity I/O license to get your individual channel information to/from the Unity Server, and you'll also need a multi-channel audio I/O device, purchased from Unity or other third party vendors. Almost any PC audio interface that works with a Mac will be fine. We like Focusrite's Clarett 8Pre using USB.

    The main thing to keep in mind is 'don't send Unity back it's own audio'. For example, if you send the audio from Unity channel 1 out of your PC interface on output 1, make sure it does not appear at any input of the interface. If you do, you'll get a nasty slap-back echo that will drive you crazy.

    Some people have solved this by sending Unity channel 1 information to the program feed input on their existing Com system, and their program feed is sent into channel 1 on their 2-wire system. They then talk on channel 2 of their 2-wire system. They listen on both channels. Channel 2 of the 2-wire system is sent back to Unity. The problem with this situation is that you tie up both channels on your existing 2-wire system. If this isn't a problem, then it's certainly a workable solution.

    A better situation is to use a 2 to 4 wire interface device available from several manufacturers. RTS makes an SSA-324 Analog System-to-System Adapter that works fairly well with both RTS and Clearcom systems. Studio Technologies also makes the Model 45DC (for Clear-Com) or Model 45DR (for RTS) 2-Wire to 4-Wire interface, which has a bit higher performance and works with several 2-wire systems on the market, including those from RTS and Clearcom. Both of these devices provide 'nulling', which simply means that most of the audio sent into the system is removed when received back. While not a perfect solution to the digital echo problem, it is definitely a workable solution to maintaining both channels of a legacy 2-wire system.

    Additionally, there is a nice low-cost solution from Pro Intercom, their model AD903 adapter. This is by far the most cost-effective solution of the three interfaces.
    Last edited by MikeM; 3 weeks ago.

  • #2
    A diagram showing a basic Unity Intercom being interfaced with a third-party comm system and a diagram showing A&E's Live PD TV Show being interfaced with Unity Intercom
    Attached Files
    Last edited by MikeM; 05-12-2017, 09:33 AM.


    • #3
      This was created by the TV Station KSHB Action News to demonstrate how Unity Intercom had been integrated in their existing comm infrastructure.
      This is a case study with KSHB Action 41 News using Unity Intercom. We asked the station to share the details of how they were using Unity. The following Article and Video was created by the TV station to demonstrate how Unity Intercom had been integrated in their existing infrastructure and how it has positively changed the way they communicate.


      • #4
        Have you tried the ST 45DC or DR as a combo Audio Interface/4W to 2W? If not, is there any reason it wouldn't work?


        • #5
          We haven't used that particular interface, but if you're already using Unity with the Dante Virtual Soundcard there's no reason that this wouldn't work just fine.


          • #6
            Yeah. Just haven't seen any other combo soundcard/4w to 2w interfaces, so this would be pretty slick.


            • #7
              Mr X., did you ever evaluate the ST 45DC as an interface?


              • #8
                Originally posted by JosephAdams View Post
                Mr X., did you ever evaluate the ST 45DC as an interface?
                Not yet. Might have an opportunity to try this in 2017.


                • #9
                  I reached out to Studio Technologies and received this very helpful response in regards to interfacing Unity to my ClearCom MS-704:

                  I'm not aware of anyone doing specifically what you are asking about. But I think that it should work.

                  I checked and the MS-704 is a 4-channel main station that provides power and audio for four channels of Clear-Com-type single-channel party-line intercom. One Model 45DC can directly connect to two of the four PL channels and convert them to two send and two receive Dante audio channels. If desired, use two Model 45DC units to link to all four PL channels. You would power each Model 45DC unit either through a PoE port on the associated Ethernet switch or an optional 12 volt power supply. (Our power supply is order code PS-DC-02.)

                  You would get the Unity Intercom Base license, add the number of Unity user licenses you'll need, and then add the Unity I/O License. You'll license a copy of Dante Virtual Sound Card (DVS) software from Audinate. You'll install the Unity and DVS software in a Mac. Using the Dante Controller application (free) running on the Mac you'll route (make subscriptions) the Model 45DC's audio signals to/from the DVS that's also running in the Mac. Then finally you'll use the Unity configuration tool to route the desired audio signals between DVS and the Unity intercom I/O function.

                  So it seems to me that it will work fine. You could double-check with Unity but I'm pretty comfortable that you should get excellent performance.
                  I hope this helps! I am putting together a proposal and will hopefully have an opportunity also in 2017 to try this out.



                  • #10

                    Did you get to try the 45DC yet? We are about to get one for our com system and it would be great to know if it works. We already use Dante to tie Unity to parts of our Clear com and Program feed from FOH and it works great. Thanks!!


                    • #11
                      Joseph, we still don't know of anybody directly using the 45DC, but given the fact that Studio Technologies makes great stuff, this particular piece of gear looks like it would be fantastic. I have a question for you though: you mention that you're using Dante to connect to parts of your Clearcom system. Can you elaborate on how you're doing this? Are you perhaps using the new Clearcom Dante interface card for a Clearcom matrix intercom, or is this something completely different.

                      Given the low cost of the Dante Virtual Soundcard for the Mac, the 45DC actually seems like a fairly inexpensive solution to get 'nulled' audio in and out of existing Com systems, plus it has the benefit of using Studio Technologies great nulling circuitry. Seems like a win-win.


                      • #12
                        I haven't gotten approval for the project yet but hope to do this soon. I'm going to rack mount a Mac mini, get two ST45DC's plus the Unity licensing and Dante virtual soundcard. Exactly as I laid it out. Happy to write up a full report once I get it going. Good luck!


                        • #13
                          Hey guys, happy to report that I've installed the equipment as I laid it out back in December, putting all 4 partyline channels on the network with Dante. It works great. We are a church with two auditoriums so the nice thing is that by using this platform, I can also bring in program audio feeds over Dante as well as I have some I/O boxes at each FOH. Users on the Unity system can now listen to either program feed just by choosing it.

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                          Just to recap:
                          • Using two Studio Technologies 45DCs to connect all four Clearcom partyline channels. I ran mine through our intercom patchbay just in case I want to repatch it down the road for some reason.
                          • Dedicated Mac Mini in the rack running Unity Server and Dante Virtual Soundcard with the I/O license. Also using the Advanced Program Feed license and sending in a feed from both auditoriums.
                          Our next steps will be to set up the networking so that we can access Unity server from cellular as well as internal. Any questions, let me know and I would be happy to help if I can. Thanks!