Abstract: An asynchronous transfer mode switching arrangement includes a serial to parallel converter arranged to receive input packets of data, which include routing information, in serial form and convert the packets of data to parallel form. A first random access memory is provided in which each packet of data is entered at an addressed location into the memory, and the address is entered in a respective first-in first-out output queue at the tail. The address at the head of the queue is accessed and the packet of data is read from the first random access memory into a parallel to serial converter and the packet of data is serially delivered to the associated output. The first random access memory and the output queues are controlled by a memory management arrangement to which is connected a broadcast channel routine second random access memory.

Abstract: The invention concerns apparatus for monitoring optical fibers by detecting variations in the polarization of light being transmitted through the fibers. In one embodiment the optical fibre carries non-coherent light and the incoming light is split by a passive splitter (2) connected to a polarization beam splitter (5). Variations in the output of this polarization beam splitter are detected, amplified and filtered so that they can be compared with a preset reference voltage. A counter (12) is used to detect variations. Another embodiment relates to the detection of polarization variations in coherent systems.

Abstract: A circuit protection device designed to protect a pair of electrical circuits by fracturing at such time as an overcurrent condition has occurred in a first of the circuits, this novel device comprising a substantially flat substrate of non-conductive, frangible material upon which a resistive component and a fuse conductor reside in an adjacent relationship on a common surface. The resistive component is part of a first circuit, and the fuse conductor is part of a second circuit. The resistive component, at the time of an overcurrent therethrough, becomes hot and causes a heating of the near surface of the frangible substrate.

Abstract: A system for interconnection of a stack of circuit boards, wherein each of at least a plurality of the circuit boards has an end region carrying one or more light transmitters or light receivers, an optical structure forming an interconnecting backplane for the circuit boards, the optical structure comprising a first surface carrying a multiplicity of hologram elements disposed to receive light beams from said light transmitters and to route said light beams to a second reflective surface where said light beams are reflected back to said hologram elements for routing to said light receivers.

Abstract: The invention concerns a method of pointer processing a digital TDM data stream at a node of a synchronous SDH transmission network so as to justify the data stream on transmission, the data stream having a specified line frequency and being composed of frames, each frame containing a reference word, and the node of the transmission network having a node frequency, the method comprising storing the incoming data stream in a buffer store at the node, using the line reference of the incoming data stream to extract a data pointer from the data stream for each frame, which data pointer indicates the location of the reference word of that frame in the buffer store, and characterized in that a timing pointer is extracted from the incoming data stream utilizing the line reference and a line clock the frequency of which is a multiple of the line reference; the timing pointer so extracted is converted into a reference value by utilizing the node reference and a node clock; the reference value is utilized to generate a