Yealink T46U - audio and connection issues

[shavu]

Hi,

I am trying to troubleshoot a problem I can't even isolate between the phone, pbx, and sip vendor. I have opened a ticket with sip vendor about dropped calls. Though I think this has to do with the phones and/or 3cx pbx. I have 2 centers in different suburbs and using 3cx ent/ai for 8c calls with 2 DIDs from a telco. This phone system was hosted and managed by a different vendor including telco without issues until 3/2026 when I switched to 3cx (had to change due to cost, they were good ). I admit I don't understand pbx as much as I need to. Thanks to the community I was able to resolve all my previous problems. The one persisting issue is random garbled audio, dropped calls, and phone dropping connection to the pbx. Please keep in mind, these used to work without issues for both sites pre-3cx switch. Both networks are different, verizon and cox. All the phones are Yealink and only 3 are not T46U. Please help me identify where to look for the problem. Thank you.

 

[SteveITS]

Does the firewall test pass on the server?

Are these set up as router phones or using an SBC?

Try the connection/call quality monitor and see what it says for problem calls.

 

[shavu]

Hi,
Thanks for your reply.
This is hosted by 3cx so I have to see if it passes from a phone? The calls are coming in/out, just random audio quality or drop calls. 14 phones passes through Yealink T57W router phone on 1 site. The other site passes through T46U.
Does the connection quality function only works on the user's login account or can that me initiated from an admin account. Only I have a login credential to my own extension just to manage. The main extension does not have a login account. Thank you.

 

[JohnS_3CX]

14 phones passes through Yealink T57W router phone on 1 site. The other site passes through T46U.

Too many phones behind a single router. Either install a dedicated SBC at each site (highly recommended), or at least convert more of your T5/T4U series phones to routers so they can each handle their own traffic or spread out the load to under 5 phones per router.

Eliminate this bottleneck first before your troubleshoot further to avoid chasing shadows.

 

[shavu]

I initially had it that way, but the calls were bad. That's why I bought the T57W and used only one phone router.

 

[SteveITS]

This is hosted by 3cx so I have to see if it passes from a phone?

No, there's a test in the admin panel but it's not a concern if it's 3CX hosting.

3CX used to say router phones could handle up to 10 so either way 14 is too many. You can have multiple router phones per location, or they could all be router phones.

 

[shavu]

Ok. I will switch back to how I had it and see. Thank you.

 

[shavu]

I called the center, she can hear me clear, but I from my end I it's not as clear. The "details" from below regarding RTCP doesn't look good. hard to say it's the firewall since didn't have any issues with call quality with the last provider. Both network configured differently with different ISP and routers, yet both having the same issues.

 

[KyriacosS_3CX]

Hi,

You could raise the issue with Voxtelesys as well, perhaps they can view something on their end - A question, are you using the 3CX build in template for this SIP Trunk?

 

[Kevin@voxtelesys]

@shavu you said you had a ticket open with Voxtelesys, can you share that ticket ID with me in a DM?