Why should Isolation be used in the IP telephones?
The Power-Hub channels are not isolated from each other. [This is not required and would become very expensive]. This means that two terminals that are connected to ground, could be at different potentials and cause damage to the Power-Hub via Ground Loops. If a terminal does not have any external connections, which could be connected to ground, then it does not need to be isolated. i.e. the casing (if plastic) is acceptable isolation.
