Abstract: An ATM telecommunications switch includes a plurality of parallel data switching planes and a parallel central plane, each plane having an equal number of input ports and output ports and a central switching unit to switch each input port to any output port. The switch further includes a first rotator to connect each input port cyclically to each timeslot of the central switching unit and a second rotator to connect each timeslot of the central switching unit cyclically to each output port.

Abstract: Packet based telecommunications networks are being developed to carry Constant Bit Rate (CBR) data streams between source and destination exchanges in the form of multiplexed packets, which are recombined at the destination exchange into a CBR stream. In such a network it is desirable to synchronise the frequency and maintain the phase relation of the recombined CBR stream with those of a source CBR stream arriving at the source exchange. The described synchronising circuit for use in such a network comprises a local oscillator (46), a local Residual Time Stamp (RTS) generator (50) arranged to determine a local RTS value (51) from the local oscillator frequency, a comparator (52) to determine the difference between the local RTS value (51) and a source RTS value (41) extracted from packets received at a destination exchange (10), and an oscillator controller (54) responsive to the difference to adjust the frequency and phase of the local oscillator to maintain the difference constant.

Abstract: A telephony system includes a plurality of local network terminations connected to a street cabinet in turn connected to an exchange. The street cabinet has a power supply for supplying voltage, a clock for generating a master ringer signal, and a modulator for modulating the voltage with the ringer signal. The filters extract the DC voltage and the ringer signal. The extracted DC voltage and the extracted ringer signal obviate the prior art requirements to provide a separate DC power supply and a separate clock within each local network termination, thereby avoiding duplication of components within each local network termination.

Abstract: A communications system employs a high-speed digital link with discrete multiple tone (DMT) the outward paths from a central transmitter/receiver to further transmitter/receivers receiving signals therefrom using one set of carrier frequency channels and the return signal paths using a different set of carrier frequency channels.In one form the central transmitter/receiver is an exchange and the further transmitter/receivers are subscribers connected to the exchange.

Abstract: A telecommunication network and switching system where digital circuits are supplied to customer terminals for dial-up services and where automatic testing of the access connections to the customer premises is performed while calls are not in progress. A loop test unit is provided at the customer's premises near to the customer digital line terminals able to detect a test sequence sent from an exchange when a call is not in progress, the test sequence being recognized by the loop test unit and a test sequence being returned to the exchange to enable the error performance of the link in both directions to be tested.

Abstract: A telephone line power strip-off circuit includes a low loss polarity guard sub-circuit, a low loss line seize sub-circuit, a low loss speech transformer sub-circuit and a high efficiency switched mode power supply which has an output voltage less than the input voltage, arranged to recover 80% approximately of the power presented to the terminals of the phone.

Abstract: In a telecommunications switching network which has a plurality of sub-networks, each sub-network having a plurality of User Network Ports, the Destination and Source addresses in a cell-header carrier by a cell switched by the network are each divided into a Port Address part and a Sub-Network Address part, the Source Sub-Network part being implicit while the cell remains in the Source Sub-Network and similarly the Destination Sub-Network part is implicit when the cell arrives in the Destination Sub-Network, the Source and the Destination Sub-Networks being linked via a Cross-connect switching device wherein the address formats are changed.

Abstract: In a telecommunications duplicated synchronous switch where switching in bit synchronism is carried out and fault detection is by discrepancy checking between the duplicate switch planes, determination of the faulty plane is provided by the data being carried in switched bytes grouped into data frames, each frame carrying check data in respect of data from an earlier frame. Corruption of data in a frame is thus indicated by information in a later frame.

Abstract: A multi-stage telecommunications switch, such as a "rotator", has 2.sup.n input ports and 2.sup.n output ports, `n` being an integer greater than 1, and is formed from a number n.times.y.sup.(n-1) of y.times.y switching elements where `y` is an integer greater than 1 and the elements are arranged in n stages wherein each switching element within a stage x, where `x` is an integer between 1 and n, changes state every y.sup.(x-1) timeslots to provide switching only in the space domain. The switching elements may be electrical or optical devices.

Abstract: In a telecommunications system in which narrowband or guiding services already exist, different service rates, either fixed or variable may be required. A further service switch is connected in parallel with the existing narrowband or guiding switch, the further service switch being similarly controlled in response to the guiding signalling.

Abstract: A telecommunications system has subscriber and/or private automatic branch exchange accesses, an access signalling system, and a connectionless network signalling system. The telecommunications system employs a connectionless signalling interworking unit for controlling the access signalling system remotely from the accesses. The unit is operative for interworking the network signalling system and the access signalling system. The unit includes a transaction control and transaction monitoring function for passing information bi-directionally between network points without establishing a bearer connection between the network points.

Abstract: A method of on-air registration of a cordless telephone handset with a base station, includes the steps of: arming the handset so that it can indicate that it wants to register with a base station; arming the network to enable it to accept the registration request from the handset; activating the handset to start transmitting link request words; causing the base station and the associated network to determine that the link set-up is to be used for registration purposes, causing the base station to use the handset's identity to decide if that handset has a pending registration request, and transferring into the handset the registration details over the established link.

Abstract: In a multi-station, demand assigned, time division multiple access system, digital information is communicated from a head end to a population of outstations so that all the outstations receive the stone stream of digital information and select their traffic from it. Traffic is only sent to and from an outstation when there is a demand for it. As the outstations are at random ranges from the head end, it is necessary to know the times of travel for bursts of information so they arrive at the head end sequentially. Free time in each frame is consolidated and made available for ranging-in outstations.

Abstract: An ATM telecommunications switch includes a plurality of parallel data switching planes and a parallel control plane, each plane having an equal number of input ports and output ports and a central switching unit to switch each input port to any output port. A single data stream is divided between a plurality of input ports and the data is concatenated from a plurality of output ports to reconstitute the data stream. A first rotator connects each input port cyclically to each timelslot of the central switching unit and a second rotator connects each timeslot of the central switching unit cyclically to each output port.

Abstract: Timing pointer signals to be transmitted across a synchronous digital hierarcy (SDH) network are transmitted in virtual containers (VC) in a number of fixed stuff bytes which were hitherto unused. In a preferred embodiment two such bytes are used to carry the timing information which allows for up to a sixteen bit code to be provided for the timing pointers.

Abstract: A method for providing dynamic allocation of trunk circuits of different classes of traffic having different bandwidths in a Digital Private Network Signalling System (DPNSS) link between two switching nodes is disclosed. The trunk circuits are grouped into trunk groups. Trunk Access Class (TAC) is a code used to differentiate different classes of traffic. In the switching nodes, a table exists which defines to which trunk groups access is allowed or barred by TAC whereby bandwidth (or trunks) in the DPNSS link can be allocated by class of traffic. The grouping of trunks into trunk groups and the table which allows or bars access to trunk groups by TAC may be altered from time to time in the switching nodes at each end of the link by management command, to vary the allocation of bandwidth between classes of traffic in the DPNSS link.

Abstract: Data is protected in a data transmission system operating on the synchronous digital hierarchy. The data is transmitted in multiplex form between ports in the system and protection is applied between ports at different or the same aggregate bit rates. This protection is achieved by selecting between individual portions of the payload within the aggregate signals and each part of mutually protective portions has the same nominal traffic capacity. By duplexing an alternative signal path is created to ensure a continuity of traffic through the system in the event of a fault in one path.

Abstract: A telecommunications switching device includes a plurality of ports and a plurality of switching units and a connecting circuit for connecting each of the ports to each of the switching units in turn. The connecting circuit includes a photonic channel separation circuit and a photonic space switching circuit.

Abstract: Apparatus is disclosed for use in the testing of the electromagnetic compatibility (EMC) and electrostatic discharge (ESD) performance of an electrical unit. The apparatus comprises a cable tray positioned adjacent the unit, the cable tray having arranged upon it cabling which is representative of the normal cable installation for the unit and in which the cabling is connected to the unit. A cable tray base plate may also be provided. The cable tray is pivotally, and detachably, mounted to the base plate such that the orientation of the cable tray with respect to the base plate is adjustable.

Abstract: A reconfigurable switch memory which is applicable to time switches and space switches enables two very different time switching functions to be efficiently implemented by one type of switching unit. A reconfigurable switching device is provided which, for instance, can work in either one bit or five bit mode, the granularity of the switch being varied.