Abstract: For external terminals, telephone number information is provided internally in a private branch exchange. Upon call setup, signalling information is checked to determine if telephone number information is internally present in the private branch exchange to a user of a B-channel in an ISDN system. As warranted, dialing of the telephone number is initiated by a system controller in the private branch exchange.

Abstract: Method for establishing a telecommunication connection wherein a calling party at a first telecommunication terminal station external to a private branch exchange (PBX) sets up a first connection to the PBX via a public telecommunication network and transmits information to the PBX which indicates, inter alia, a telephone number of a second telecommunication terminal station. In response, the PBX sets up a telecommunication connection between the first telecommunication terminal station and the second terminal station and, in addition, the PBX stores information relating to call charges resulting from the connection to the second terminal station.

Abstract: The hash result of useful data is transmitted to a multiply-protected central server in which it is transformed into a signature on the basis of a crypto operations system combination with a private key code of the originator. The signature is deposited in the central server and is available as what is referred to as a "digital signature" for the transmission of the useful data.