If you use configuration files, the OS79XX.TXT file no longer controls the image used by the phone. Image version and upgrading is done through the image_version configuration parameter in the configuration files. In the startup, each SIP IP phone attempts to download the SIPDefault.cnf configuration file. This file contains the image_version parameter that tells the phone which image to run. Therefore, if you attempt to load the SIP version 7.1 software, SIPDefault.cnf must contain image_version: P0S3-07-1-00. If the image load differs from the one that is currently loaded on the phone, the phone contacts the TFTP server to convert to the new image.
