We can't use extension modules on the 6739i using POE powering. They do work only if the power adaptor is connected. The extension modules simply do not power on if using POE. This is quite strange, as the phone consomption is only about 6-7 watts. So there is enough POE power remaining for the extension modules. The 6739i is seen as class 3 POE device by the switch where it is connected. The switch can deliver 18W, but 12.95W is enough to power a class 3 device. So the extension modules should work with POE. This is a terrible situation, i hope this will be corrected asap because using a power adaptor or external 48V POE splitter is simply not realistic in highly professional installations where this costly phone will be mostly used. Aastra, can you give clarifications about this POE (hardware ?) problem ?