Abstract: A radiotelelphone system in the form of a private branch exchange (12) within and/or outside one or more buildings is equipped with a plurality of mobile subscriber units (28), a plurality of transmitter/receiver units (27) capable of communicating with the subscriber units (28) by radio, and a central unit (26) cooperating with the transmitter/receiver units (27). In order that such a radiotelephone system not only permits mobile telephoning within and/or outside buildings but also can be installed later and adapted to changing requirements in a simple manner, the transmitter/receiver units (27) are arranged and designed to form not only a radio link to at least one of the subscriber units (28) but also, via respective adjacent transmitter/receiver units (27), a radio-link chain (radio bus) to the central unit (26), which has a separate transmitter/receiver unit.