Abstract: The invention relates to an arrangement for acquisition of services via a telephone set. The arrangement comprises a communication element which connects the calling service purchaser to a service provider station with associated computer equipment. The arrangement contains a reader unit which operates in conjunction with an identity element for communicating with the computer equipment. The identity element is provided with information for identifying the purchaser. The identity element is preferably a smart card and the communication element comprises a reader unit which, together with software, can handle smart cards. The arrangement has a built-in keyboard for feeding in data.

Abstract: The invention relates to a means for identification and exchange of encryption keys between communicating apparatuses for encrypted transmissions. The means comprises a card reader for smart cards connected to the communication apparatus which may be a telecommunication apparatus, e.g. of telephone or facsimile type. The reader can communicate with another reader at a called telecommunication apparatus. For identification and exchange of encryption keys the required calculations are performed by the reader or the smart card using data stored on the smart card in a protected field with limited access. The means enable intercommunication between products of different makes owing to a standard identification procedure and exchange of encryption keys.

Abstract: An electronic speech circuit for a central battery telephone set in the form of a Wheatstone bridge has for one arm of the bridge the impedance of the incoming line to the set and for another arm an impedance mainly equal to the line impedance. The remaining arms consist of resistance impedances, preferably resistors. The DC-terminals of the transmitter amplifier are connected in the bridge diagonal which is connected between the two resistors, and the other bridge diagonal is formed by the signal path of the receiver amplifier, the DC-terminals of which are connected to one of the resistors and to the line simulating impedance.