An ISDN private branch exchange line group is activated by the telephone network provider at the telephone switch and allows several ISDN point-to-multipoint connections to be reached under a single telephone number. The ISDN connections are technically interconnected to a single virtual connection. Combining three point-to-multipoint connections, for example, the subscriber has up to six B-channels for parallel calls. Depending on the connection and telephone network, incoming calls are indicated alternating or simultaneously. The availability of convenience features may be limited with this type of connection.