The Hybrid Balance refers to the Echo on Analog Loop Start Trunks. While I do have Analog Loop Start Trunks, I should clarify that the feedback is a static noise on outgoing calls. I believe the caller hears the static, but the receiver does not. I should point out that they are using 6900 SIP phones. I know 6900's are not ideal for the Mitel 250 system, but that is what they wanted. I know there is the feature code 320 for Audio Diagnostic and it leads you through a prompt where you can choose static. I am trying to figure it out with out interrupting the client.