Troubleshooting no ringback voice gateway

Question

Hi all,
I'd like to ask about voice gateway that installed on my customer site. below is the topology:
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PSTN – Voice Gateway – C2960-48PST-L – Callmanager and IP Phone
                                                           |
                                                           |(FO)
Analog phone – PBX.A – Voice Gateway –––– Voice Gateway – PBX.B – Analog phone
the problem is that there's no ring back tone when calling to another site analog phone from ip phone/analog phone. The PBX (NEC) are using E1 connection to the router. Does the ringback provided by PBX or the Voice gateway?
Thanks in advance
Dias

Answer 1

Yes, we did find a solution. It ended up it was on the carrier's end. I believe that they were generating ring back inbound to calls we originated, but not outbound to calls originated from the carriers. They switched that so that they did not send us ring back, but did send carriers ring back for inbound calls and that appeared to solve the issue.
Here's my carrier's explanation in case that wasn't confusing enough: "We made in-band tone available to the SIP trunk via an egress profile change on the SONUS Gateway. Early-media is determined / initiated by
the called or far-end switch."