product description cisco ip phone 8841 voip phone product type voip phone compatible platforms cisco business edition 6000 main features multiple voip protocol support integrated ethernet switch voip protocols sip rtcp rtp srtp sdp voice codecs g722 g729a g711u g711a ilbc isac lines supported 5 lines intercom yes speakerphone yes digital duplex call services voice mail caller id call waiting call forwarding call transfer call hold message