Hi all, Firsts of all, let me say that I'm new to asterisk. I have some time suscribed to the list reading a lot of your messages and trying to learn a lot. The case is: last week I installed an asterisk server in the following scenario: PBX --- CISCO_ROUTER ---- ASTERISK The calls that are routed within the asterisk work perfect, there is not problem. However, the calls that are from Asterisk to the PBX (or viceversa) have a kind of noise every three seconds or so. I have tried different codecs without success and I don't know what else to try. In this moment I only count with the codecs g711ulaw and g711alaw in the router, I don't think bandwidth is a problem in this moment. This is the output while a call is been used: ---- cut here ---- VoIP*CLI> sip show channels Peer User/ANR Call ID Seq (Tx/Rx) Form Hold Last Message X.Y.Z.K 2. 83E9477C-3A 00101/00101 ulaw No Rx: ACK 1 active SIP channels ---- cut here ---- And this is an small excerpt of my router: --- cut here --- dial-peer voice 11 voip application voip_asterisk destination-pattern 280. session protocol sipv2 session target ipv4:X.Y.Z.K codec g711ulaw ip precedence 5 --- cut here --- Can any one point me what else can I try?, what would you do in my case? Thanks a lot. Alejandro,