Abstract: A method and apparatus of phase synchronizing a plurality of spatially distributed application modules having synchronizing clocks requiring synchronization, each application module being connected, at a predetermined site nearest the module, to an outgoing path and, at a corresponding site nearest the module, a return path of a pulse reference path, the method comprising the steps of injecting reference pulses at a predetermined frequency into an injection site of the reference path such that the pulses travel along the outgoing path to a remote site and return to the injection site along the return path; determining, for each application module, the time interval for each pulse to travel from the predetermined site to the corresponding site associated with the application module; monitoring, for each application module, the elapsed time interval for each pulse to travel between the predetermined and corresponding sites associated with the application module; producing, for each application module, a local p

Abstract: A fibre sensor used for the measurement of ambient refractive index has a tapered end. The taper of the optical fibre generates cladding modes which undergo multiple reflections at the external surface of the fibre, and therefore gives high sensitivity to the ambient index. A tapered fibre is also relatively immune to contamination by adhering droplets when the end reflection is used since the droplets tend to move to the point of greatest radius, which tends to be away from the point where the Fresnel reflection of interest occurs. The reflection from the tapered end of a multimode fibre is measured as a function of ambient refractive index. In contrast to a square-cleaved fibre, the reflection from a tapered fibre is monotonically related to the ambient index, removing an ambiguity that occurs when refractive index is measured by Fresnel reflection at normal incidence. Tapered optical fibres are suitable for probes to identify the interface between immiscible liquids.

Abstract: A method for determining the highest, common bi-directional transmission rate between two stations of an ISDN communications link includes the steps of a) selecting a candidate transmission rate from a range of candidate transmission rates, b) transmitting a test signal at the candidate transmission rate through an attenuator along the link from one of the stations to the other of the stations for a first predetermined time interval, c) determining whether a return signal transmitted by the other station over the link and at the candidate transmission rate has been correctly received at the one station, d) repeating steps a), b) and c) until predetermined criteria have been satisfied; and e) storing the highest candidate transmission rate for which a return signal at that rate was correctly received within the first time interval; and f) removing the attenuator for final verification of operation.

Abstract: A method of modulating a DS3 signal for addition thereto of an auxiliary, transparent signalling channel, the DS3 signal having framing bits which provide a predetermined pattern for which frame-finding circuits hunt to demultiplex the payload of the DS3 signal. The method comprises cyclically forcing an framing-bit error onto every D-spaced framing-bit of the DS3 signal during an initial ON period of an ON-oFF modulation cycle, the ON period and the modulation cycle having lengths such that no more than two verification attempts are required to complete reframing of the signal in the presence of the framing-bit modulation, and wherein the Modulation Spacing, D, is selected so as to provide a low probability of coincidence between the framing-bit Modulation Spacing and a verification window following a secondary reframing hunt.

Abstract: A method and apparatus of restoring communications between a pair of nodes in a network having an arbitrary number of nodes and an arbitrary number of spans interconnecting the nodes, each span having working circuits between nodes designated for transmitting actual communications traffic and spare circuits capable of, but not designated for, transmitting actual communications traffic, the method comprising the steps of (a) establishing one or more independent communication paths between the pair of nodes through a series of spare circuits of spans interconnecting the pair of nodes and other interconnected nodes in the network; and (b) redirecting communications traffic intended for one or more failed spans interconnecting the pair of nodes through one or more of the paths.

Abstract: A series of nodes in a telecommunications network are connected by a bi-directional transmission path. An outgoing signal passes each of the intermediate nodes in the path and sets a counter timing at each intermediate node. The outgoing signal then returns from the loop node with time information attached to it. As the returning trigger signal passes the intermediate nodes, the intermediate nodes stop counting the elapsed time since the trigger signal passed the intermediate node, and latches the time information. Precision time synchronization information is then determined for each intermediate node by halfing the two way travel time from the intermediate node to the loop node, adjusting for propagation and processing delays, and adding it to the time information from the loop node.