Anyone Know Whether Cable Terminators Are Required for nbn HFC Split Cable Setups?

I understand this is a bargain site, but there are lots with various experiences and professions on here so thought I'd ask here first.

My wife has a new work-from home role (Nurse-on-call) and needed to have a direct nbn phone line and 4G backup so we've unfortunately had to move from AussieBB back to Telstra.

Every now and then the phone line makes lots of noise during the call and she then can't hear the other person on the line. The other person can hear her fine. The problem is not something that occurs all the time or on demand. The problem occurred a few times on Friday, nothing yesterday and once today. One time it rectified itself, but the other times she had to hang up and contact the person back again. Different people one the line each time.

I'm trying to narrow down where the problem is, low hanging fruit first so I'm replacing the phone cable tomorrow. I'm also wondering if it might be HFC cable related. E.g. I have an HFC cable with a splitter, so one end goes to the TV area and one to the office. This cable was once used with Telstra Internet / Foxtel and is now being used for the NBN. One of the ends of the HFC cable is not connected to anything. Is there supposed to be some sort of terminator plugged in the end or is it ok to just leave it open?

I see there are terminators like this, but I don't know what their purpose is and whether adding one will cause other problems. I didn't find any other info from a Google search regarding the terminators.


  • +1 vote

    What kind of noise does your wife hear? Scratchy? Under water? Dropping in and out? When it starts, does it continue until the end of the call or does it come and go?

    What kind of phone do you have hooked into the modem, too? Cordless? wired? Tried a different phone yet?

    Also, does it happen on 4G backup, or NBN, or both? (unplug NBN connection to force a 4G backup to test)

    Cable terminators won't be needed, she would be using Voip via your Telstra modem so I would focus on that first.

    • The other times it was a scratchy noise, but the problem just reoccurred and she said that this time it was stuttery - e.g. she could kind of hear but it was breaking up so much you couldn't understand them. The person said that they could hear my wife clearly (we know this because my wife is in training and there is another Medibank person on the line listening). Only once has it actually gone back to normal without her doing anything, the other times seemed to require her to disconnect and call the client back.

      The phone is a Interquartz IQ335 which was supplied by Medibank (it's their nurse-on-call service). It's corded to the Gen 2 Telstra modem. We don't have a different phone to try. She is also using a headset but I forgot to ask her whether she had picked up the handset to see if it was noisy in there too, I have asked her to try this when it next occurs.

      At the time the problems have occurred, I haven't checked to see whether the NBN connection had disconnected (whether it was on 4G). This morning we did basic testing (switching off the NBN Arris modem) to see what occurs to an active phone call. The phone line just goes dead and the call hangs up. Within a minute or so the 4G connection had kicked in and re-calling from a mobile to the landline worked fine. UPDATE: When the problem just reoccurred, I checked and saw that it wasn't switched to the 4G backup.

      I also replaced the phone cable this morning, just in case. It was only $13 so not a huge outlay. The problem has now reoccurred since changing that, so this is not the problem.

      The list of things I have yet to check are:

      1. Telstra line test. This needs to be planned to be done at a time when she is not working.
      2. Potential fault with the phone / headset hardware. Can determine if headset is a problem by checking handset when the problem occurs. Checking the phone will be more tricky as we'd need to ask for a replacement from Medibank.
      3. Potential fault with Medibank system. I'm making an assumption here, but I'm expect the calls are being directed through a Medibank VoIP system so that they can have another of their staff on the same phone call. I don't know the mechanics of this yet.
      • It won't be anything to do with the line/connection quality, likely some sort of bug/incompatibility between the VoIP server and the telstra modem. The phone handset is just a dumb speaker/microphone.

  • Did you call Telstra and ask them to run a line test and see if there is any fault on the line?

  • just disconnect the splitter and plug the one being used directly into the wall socket, since you said one isn't being used.

    • The HFC splitter is under the house. We don't have wall sockets, just the cable coming up through a small hole in the floor at a couple of locations (carpet over plywood floor).

  • Garbled VoIP is nothing to do with the cable.

  • Interesting that you'd bother with a landline at all and not just use a mobile.

    • I would never have a fixed landline by choice now, but unfortunately Medibank requires it and they don't allow just any VoIP provider and it must have 4G backup.

      Her shifts are 10 hours or so if I recall correctly so a mobile would be out of the question.

  • the phone goes through a digital line it has nothing to do with the HFC termination I guess…

  • I can probably help here.

    A couple of the other replies are correct in that the HFC cable is not the likely culprit here, although it can't be altogether ruled out if it is affecting the quality of your Internet connection in some way.

    You are using the VoIP feature in your Telstra modem. This converts the analog phone signal into a digital signal (using the SIP standard) that is carried over the Internet to a SIP server. VoIP will exhibit the sort of noises that you are describing if the connection to the SIP server is interrupted in some way (congestion, not enough speed, too much latency, etc). It can affect one just direction or both, since the upstream and downstream flow of bits between your modem and the Internet are separate streams of data.

    So, the first thing to do is work out if your connection quality is okay. When your wife next experiences these issues, log into your Telstra modem and take a look at the connection status. Make sure that the connection speed is still reporting the correct speed and there are no errors. Then do a speedtest using or You should have a latency (ping) of less than 50ms (around 10-20 is ideal) and the speed should be close to whatever you are paying for from Telstra. If there are issues with your connection, then speak to Telstra and report what you have found in detail. You may need to log issues over a few days if it's intermittent.

    If the connection is fine, then there are two avenues you can go down. Firstly, speak to Telstra to get their help with ensuring the modem is set up properly with QoS (Quality Of Service) settings. This will ensure that VoIP calls are given the highest priority on your Internet connection so that other kinds of traffic (eg streaming) do not interfere.

    If that doesn't fix it, then it's a little more complicated as you'll need to delve into the SIP (VoIP) settings within the modem - there is a lot that can be tweaked but it needs a bit of know-how. This is where you are best served by speaking with whoever is managing the SIP server. If the modem has been configured to connect to your wife's workplace SIP server, then they are the ones who need to step in and troubleshoot. If you are using Telstra's VoIP service that comes with your NBN connection (with work calls forwarded to your home VoIP number), then you'll need Telstra's help.

    Hope that helps.

    • Thanks for the detailed and interesting reply, definitely helps with understanding the flow.

      The Telstra modem does have a call log under Telephony that shows Jitter / Latency, Packet Loss values but they don't show any problems. Jitter shows values from 0 to 4 during these problem calls (from a Google search it looks like above 30 would start to be a problem) and Latency and Packet Loss values are always zero for every single call. That's not to say there isn't a problem, just that this particular call log doesn't indicate any.

      We have not made any changes to settings of the modem to connect to anything Medibank related so I expect our modem still goes to the Telstra SIP server.

      As a random FY: My wife said that the garbled/static noise generated only occurs when somebody at the other end speaks, rather than a constant noise. Makes sense but clarifies my earlier statements.

      We're going to run some manual tests today but odds are we won't see it. I was hoping to just leave my mobile connected to it for an hour or two and see if the problem occurs, but that phone has no speaker phone so somebody would essentially need to have the headset/handset on to hear when the problem occurs. What a pain in the arse.

      It's quite difficult to have my wife do any checks/testing during the problem or even to call out to me that there is a problem, because she is with a client that actively needs assistance (sometimes medical) and is frantically trying to get it operational again.

      We'll see how we get on with our testing. Cheers.

  • re-direct the call to her mobile?


  • If ntd and modem leds remain green it nit a network issue its its internal. Try a different model phone. Ensure sockets are not corroded. Replace any fualty cpe.

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