Is your modem rented? If so, you can just go get another one from them.
Do you have a drop amplifier installed?
Telo with 2 Handsets, a Linx, and a Safety Phone
Telo2 with 2 Handsets and a Linx
I guess that's what I get for buying one of those refurbished Linksys CM100 modems.
1) Installed Ooma Telo between router and modem. This did not prevent the broken and delayed speaking.
2) Worked with Ooma on every possible QOS setting. I believe that QOS will not help a jitter problem if you have a large enough upload bandwidth. Jitter is a varying delay of multilple packets traveling the same network, not a shortage of bandwidth which QOS addresses.
3) Spoke with Comcast and other DSL providers. They will not guarantee jitter on a residential line. This is a big difference between a residential and business line.
4) Installed Ooma Telo after router. This did not have any improved effect.
5) Replace DOCSIS 2 modem with DOCSIS 3 modem. No effect
What I think may have fixed:
On my.ooma website, set my phone numbers to "enable fax mode". The difference between normal and fax mode is the codec that is used during a phone call. By enabling "fax mode" you are forcing a "lossless" codec that requires more bandwith, but a more stable quality call.
The normal codec is a very compressed data stream that requires about 20kbps - 40kbps to effectively communicate. Due to the compression, it has difficulty rebuilding the packets if there is any jitter or delay.
The fax mode codec is more of a "lossless" method that requires higher bandwidth of 70kbps - 90kbps. I believe that because it is lossless, it does not break up with delays in the transmission (Jitter). "Lossless" acts more like an analog line so it does not have to recreate packets digitally. The obvious downside to fax mode is the higher bandwidth requirement. Since Comcast has a relatively large upload, I am not concerned about giving up bandwidth to Ooma.
I have also owned a Vonage VOIP system and have come up with the same conclusion about bandwidth. Vonage allows a wider range of options from highly compressed to "Lossless". Ooma only offer the 2 options. Normal (Highly Compressed) or Fax Mode (Lossless). I have always found the larger bandwidth codec produces a better user experience on both ends of the line. If you have the available bandwidth.
I will update if things change. I have been running clean in fax mode for about a week.
I also have had upstream call quality problems since moving to a new home where Comcast is the only viable Internet solution. I am too far from the AT&T CO for fast DSL. It's a bummer as I have been a long time user of Ooma (used Hub/Scout since 2007).
Ooma support says my jitter has been too high at times (ranges 2-36 ms). Comcast Arris modem has no way to set QoS. So my only other solution is to try the Comcast VoIP that I get with my bundle, or get a landline. But I will see if the fax mode helps. I have had it on and off at times (sometimes set it for a fax and forgot to turn it off). Interestingly, comments about my upstream audio quality have also been sporadic.