Audio delay when call answered

[tjwesto]

I've got 4 x W56H handsets with a W60B at home connected to the Sipgate VoIP service.

When someone calls me and I answer, the caller hears an audible "beep" followed a split second later by two more "beeps" and then we can hear each other. This means that during the first couple of seconds the caller cannot hear me. This is also true when I don't answer and the call diverts to the Sipgate voicemail service. Again, the caller hears those beeps at the start of the playback of my message.

Not too sure what's happening here and whether this issue relates to the Yealink phones or the Sipgate service.

In terms of configuration the W60B sits behind my router which has NAT enabled, but I've forwarded the SIP and RTP ports.

It seems strange that the caller can hear these audible tones before we can hear each other.

Any suggestions would be gratefully received.

Thanks in advance.

Tim