Abstract: In a transmission system, a transmitter has a frame assembler which frames with a header and a payload portion. The header (22-1) comprises a validity indicator (SSSSS) to indicate the validity of a sequence of ATM cells in the frame. By using values of the validity indicator (SSSSS) different from the value of the validity indicator for valid ATM cells, it becomes possible to transport data in a format different from a sequence of ATM cells.

Abstract: A telecommunication network including a plurality of secondary stations and a primary station wherein the secondary stations a least partially share a common transmission channel to the primary station, thus obtaining high data transmission efficiency under high load conditions. To prevent interference, an access protocol is employed according to which all secondary stations which have data to transmit send transmission request signals to the primary station. The primary station then transmits to those secondary stations an allocation signal assigning respective time slots to them. The secondary stations then transmit in their assigned time slots. Directly upon completion of transmission in its assigned time slot a secondary station transmits a further transmission request signal to the primary station it such secondary station still has further data to transmit.

Abstract: In a transmission system a transmitter (2) comprises a frame assembler (8) for assembling frames with a header and a payload portion. The header (22-1) comprises a validity indicator (SSSSS) to indicate the validity of a sequence of ATM cells in the frame. By using values of the validity indicator (SSSSS) different from the value of the validity indicator for valid ATM cells, it becomes possible to transport data in a format different from a sequence of ATM cells.

Abstract: In a transmission system for transmitting synchronous data portions and asynchronous data portions, a transmission frame includes regularly spaced synchronous data portions interleaved with asynchronous data portions. To insure that the packing density of asynchronous data portions is optimal, the position of the synchronous data portions is allowed to deviate from its nominal value to increase the packing rate of the asynchronous data portions.

Abstract: A multiple access telecommunication network wherein a primary station is coupled to a plurality of secondary stations by a shared transmission medium. Depending on traffic volume it is advantageous to be able to change the type of access protocol employed by the secondary stations in order to prevent deterioration of transmission efficiency. Accordingly, the access protocol is set by the primary station by transmitting to the secondary stations a channel indicator indicating where in an uplink frame a secondary station can submit its access request. The primary station may also specify the message key which a secondary station must use when transmitting an access request. Applicable to multimedia networks using CATV systems.

Abstract: Telecommunication systems such as PON-FITL-Systems are known having a TDMA frame structure and comprising a main station and a number of substations. The known systems can comprise apparatus for coarse ranging and for fine ranging. A Pseudo Noise Sequence based coarse ranging technique employs coarse ranging at a fixed position within the upstream multiframe reserved for ranging, preferably for fine ranging. By applying a low power Pseudo Noise Sequence for coarse ranging and sampling the range in the main station only within a fine ranging window the position of which is known to the main station, a more accurate coarse ranging is achieved. Within the fine ranging window normally no data are present, and thus the signal-to-interference ratio is an order of magnitude better than in the other part of the frame.

Abstract: Telecommunication systems such as PON-FITL-Systems have a TDMA frame structure comprising a main station and a number of substations. In order to achieve accurate fine ranging, an A/D-converter for acquiring samples from a ranging pulse transmitted from the substation is operated at a frequency which is high with respect to the master or bit clock, i.e. real time oversampling occurs. Such high speed A/D-converters are expensive, consume much power and have limited resolution. Furthermore, for systems with even higher bit rates the known oversampling becomes cumbersome. A quasi-oversampled coarse and/or fine ranging is proposed operating at relatively low sampling rates. Thus the substations send a repetitive ranging-bit-pattern which is sampled in the main station and thereafter reconstructed in a processing apparatus to a quasi-oversampled ranging-bit-pattern.

Abstract: Telecommunications passive optical networks are known which employ a TDMA frame structure for transmission between a main station and a number of substations. Due to increased capacity demands and still further service demands, there is a need for higher bit rates over such networks. The invention provides a high bit rate passive optical network wherein the substations operate at only a fraction of the network bit rate, and so are hardly more complex than in lower bit rate networks. That is achieved by formation by the main station of sub-frames of the data intended for transmission to a number of the substations, and bit interleaving the sub-frames to form a data frame which is transmitted over the optical fiber cable. Each substation is adjusted to only listen to the sub-frame to which it is assigned.

Abstract: A device for writing, reading or erasing a record carrier has a coil with a winding arranged between an objective lens and the record carrier. Optical radiation is focused to a spot, the converging beam passing through the coil opening. A core of a transparent material, having an index of refraction which significantly decreases vergence of the focused beam, is placed in the winding opening. As a result the diameter of the coil can be reduced, and permit increase of the generated magnetic field.