Abstract: A record carrier having at least two information volumes recorded thereon. The first volume includes control information for use in searching for information included in that volume. In one embodiment, the first volume further includes a reference to the control information included therein in a predetermined address range, and the second volume includes substitute control information for use in searching for information in the first and second volumes and a reference to the substitute control information. The reference to the substitute control information is accommodated in a recoverable substitute address range. A reading apparatus for such a record carrier transforms a request for access to sectors in the predetermined address range of the first volume into a request for access to sectors in the substitute address range of the second volume. A method and apparatus for recording information on such a record carrier is also disclosed.

Abstract: A record carrier on which a first information volume and an additional information volume are recorded. The first information volume includes audio information, preferably recorded in accordance with the Compact Disc Digital Audio standard. The additional volume includes additional non-audio information related to the audio information recorded in the first information volume. The additional volume also includes control information for searching for information in both the first and the second information volumes. A dedicated data reading apparatus for such a record carrier firstly accesses the additional information volume. On the basis of the control information, the dedicate data reading apparatus can also access the audio information in the first information volume. An audio reading apparatus which can not handle the additional non-audio information automatically accesses the first information volume.

Abstract: A method and device for recording successive volumes of information in successive sections of a track of a record carrier of an inscribable type. At the end of each information volume a lead-out signal is recorded. The lead-out signals include control information for controlling reading of the recorded information. When the record carrier is to be read out, the lead-out signal of the last recorded information volume is first searched for and the control information therein is used for controlling reading of the information in all of the recorded information volumes.

Abstract: A bus system, comprising a bus formed by a plurality of parallel lines for data transmission handshake signals and general management signals, the bus being coupled to a central processor and to a plurality of devices for transmitting and/or receiving data signals and checking signals. The system is in the data mode when the central processor is inoperative and the system is in the command mode when the central processor is operative.

Abstract: A cryptographic validation for an external station of a communication system provided with a central data processing device, a number of access stations which are coupled thereto and a number of external stations which can be selectively coupled to the access stations. To validate an external station, the access station transmits a message encoded by a first encoding key. The external station decodes the message received and re-encodes the message using a second encoding key, transmitting the re-encoded message back to the access station. The access station then decodes this message using a second key decoder. This decoded data is compared with the data originally encoded by the access station. If the data is identical, the external station is validated.

Abstract: Transmission system for bi-phase modulated signals. Generally receiving filters for these signals will have a frequency response up to twice the bit frequency (twice 1/T) passband. For colored noise whose power increases as the frequency increases this may mean a considerable deterioration of the signal-to-noise ratio compared with the signal-to-noise ratio for unmodulated NRZ-signals. In order to increase the signal-to-noise ratio a receiving filter is used in this case, whose frequency response approximates zero above the bit frequency (1/T) (stopband) and which for lower frequencies is determined such that after filtering a predominantly three-level signal is obtained. The binary data signal can be drived from this signal by rectification and slicing. Use: Optical communication systems.