We have a new CCM 5.1 install which is connected to our legacy PBX system, which is a Siemens ISDX-S (actually formerly a Mercury PBX, but Siemens now support it). We're using two QSIG links to connect the two together.
Most things are working, but in some circumstances, calls are getting through, but are silent when they are connected. Basically, if somebody external dials a DDI for example, the call will enter the PBX (via a DASS link), then be routed out over the QSIG to the gateways. Then then gets to the phone on the IP network, which rings. The phone is answered, but neither end can hear or speak to the other. The line is for all intents and purposes, dead. It will stay 'connected' until one or other party hangs up.
This mostly happens with calls from external to DDIs on the VoIP side, and occasionally from internal PBX users to the phones on the IP side. Calls between IP phones however, are faultless, and calls OUT of the IP system are also fine, either to PBX extensions, or external numbers; external calls to the PSTN are routed over an ISDN30/E1 which is directly connected to one of the gateways. This happens randomly to. Sometimes it works, sometimes it doesn't.
Has anybody else any experience of connecting up the two systems? I've been in touch with Siemens, but they're not really turning up much info, as not many people are connecting up ISDX systems to CCM. Most are using Hipath PBXs.
Any advice gratefully received!!