Thanks to various different functions, even telephone systems can enable users to make calls at a very low cost. In general, internal calls between those directly connected to the telephone system are free. Modern Internet-based telephone systems make it possible to integrate participants into corporate communications regardless of their location, as well as allowing them to be reached via a uniform corporate telephone number. Depending on the cloud telephone system being used, these participants can also make calls to each other as virtual, internal participants, for free. Even mobile phones can be integrated into these kinds of systems, making the cost of calling them from a landline phone considerably cheaper.