I just started using Cisco's SPA112 2 line analog adaptor. When I call a Polycom SIP phone on my network the call works correctly. When I call a Yealink SIP T-28P or T-22P I have audio issues. When I call from the Yealink phone to the ATA the call works correctly. When I call from the ATA to the Yealink I have no audio from the ATA, the Yealink transmits but can't hear the ATA. I can hear from the ATA but can't send to the Yealink. The Yealin works correctly to the Polycom phones and other Yealink phones. I suppect the issue is in the Yealink but I have no idea were to look. I tried a stare and compair to the Polycom including codecs but I can't find the issue. I am using a porta 1 SIP switch for registaration.
