I just started using the SPA112, 2 line SIP to analog adapter. When I originate a call to a Polycom SIP phone, the call works correctly. When I call to a Yealink SIP T-28P or T-22P phone I have one way audio, transmit to the 500 set, no audio to the SIP phone. If I call from the Yealink phone to the 500 type phone the call works correctly. If I call SiP to SIP phone the call also works correctly. I've tried to do a stare and compair between the Polycom and Yealink phones but I can't seem to find the issue. I am regisering the devices to a Porta One softswitch. The porblem seems to be with the Yealink phones but I can't seem to find the glitch.
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