Abstract: A cellular radio system is to be implemented in an existing facility which performs switching functions and provides service features, without requiring major changes therein. Communication between the individual base stations (BS1, BS2, BS3, BS4) takes place by means of radio via existing radio channels. A cordless terminal (HS1) is assigned to a base station. If the terminal is located in the area of another base station during an incoming call, the terminal is searched for via a radio channel between the base stations. If it is found in the area of the other base station, the call is handed over to this other base station. The same applies to outgoing calls and to other functions.

Abstract: To be able to utilize the advantages of a cordless system based on the DECT standard as well as the advantages of a cellular mobile radio system based on the GSM standard, dual-mode units are known which switch automatically to the lower cost standard. The expense of such units and of the necessary additional circuits in the network infrastructure is avoided when the mobile unit and a mobile unit adapter are equipped with an infrared interface, whereby all the necessary information for the man-machine communication are transmitted independently of the standards. In this way it is possible to access the GSM mobile radio network without engaging the network infrastructure, for example with a DECT mobile unit via a GSM mobile unit adapter. The infrared interface circuit, which essentially comprises an infrared transceiver (1.1, 2.1), a codec (1.3, 2.3) and a digital signal processor (1.2, 2.

Abstract: A broadband private automatic branch exchange is to be implemented in which all broadband user stations can be switched like normal telephone terminals with all features of a conventional telephone private automatic branch exchange and without each broadband terminal requiring its own operator position. To achieve this, in accordance with the invention, all the broadband terminals (BB-E1, BB-E24) which are connectable via a broadband switching array (BB-V) to the subscriber line unit (TAE) of the public broadband network (VBN) are also connected like ordinary telephone user stations to a narrow band telephone private automatic branch exchange system (SB-PABX) which is connected via a signaling conversion module (VBNA) to the line unit (TAE) and which initiates the narrow band call setup and controls the broadband switching array for switching broadband calls.