The document provides guidance on using an 860DSPi device to troubleshoot various VoIP issues, including connection failures, network timer failures, DTMF failures, low MOS scores, speech quality failures, transmission failures, delay failures, and echo failures. For each issue, it describes typical causes and recommends tests to perform using the 860DSPi, such as VoIP RTP tests to measure MOS, latency, jitter, and packet loss and signal quality tests to identify potential plant issues. The goal is to isolate problems in the network or identify plant impairments that may be degrading voice quality.