Abstract: A distributed antenna system comprises a plurality N of spaced apart antennas 3, each antenna being connected to a RF line 2 via a circulator 4, wherein each circulator 4 is arranged to pass to its associated antenna a fraction 1/N of the RF power incident thereon.This can allow cost savings in providing the components needed for the antenna installation.

Abstract: Each wire of a subscriber's line is connected to its associated input of a subscriber's line unit by two interconnected relay contact sets. The relay contact sets are also connected to test busses. If a subscriber's line unit becomes faulty, a spare subscriber's line unit can be switched in to replace the faulty unit. The connection path is made by way of the test busses and the relay contact sets associated with the respective units. Test access paths may also be provided from the busses to the units.

Abstract: The method comprises transmitting an initiating signal in the form of a bit pattern as a continuous burst from one radio unit to the other. The pattern incorporates a preamble pattern and a security code having a plurality of bit sequences. Each sequence is transmitted a number of times. The received security code is compared with stored codes in the other unit, and if a matching pair is identified a response signal is transmitted from the other unit to said one unit. The response signal incorporates the preamble pattern for establishing synchronization between the radio units.

Abstract: Concentricity of a light-transmissive core and its cladding is measured by stimulating U-V fluorescence in the core but not the cladding, independently imaging the core/cladding boundary and the outer surface of the cladding and determining their radial separation for different angular orientations of the core and its axis.

Abstract: A transmission system in which a plurality of data streams are to be multiplexed and sent between receiving and transmitting equipment. At the transmit end the system comprises a plurality of worker tributary cards (51, 52) each having an input port (57) connected to an individual tributary to be sent to an associated multiplexer, and a stand-by tributary card (56) operative to replace a failed worker card. All the worker tributary cards (51-55) are interconnected by a common line (60) leading to the iput port (57) of the stand-by tributary card (56) but in normal operation being isolated from said line by a controllable unity-gain buffer 58.

Abstract: A system for transmitting digital data by time division multiplex (TDM) includes a transmission terminal for transmitting a TDM data stream having a frame structure which includes fixed stuff bytes and/or frame overheads forming part of the payload but not normally available to the user. The system includes a processor for locating said fixed stuff bytes, and overwriting at least some of the fixed stuff bytes to introduce mark parity, and a receive terminal having a processor for detecting the introduced parity bytes and determining whether or not there has been an error in transmission. The processor at the receive terminal includes an AND-gate to which the transmitted TDM signal containing mark parity is fed, a clock for supplying a clock signal to the AND-date, a bistable flip-flop connected to the output of the AND-gate, and a band pass filter for filtering the output of the AND-gate.

Abstract: A plurality of slide-in unit connectors are provided for receiving the slide-in units or the auxiliary slide-in units. The slide-in unit connectors are wired to at least three cable connectors in such manner that when a first cable connector only is used, each slide-in unit connector is connected to receive a respective slide-in unit, when a second cable connector only is used, one of the slide-in unit connectors is connected to receive an auxiliary slide-in unit; and when a third cable connector only is used, two of the slide-in unit connectors are connected to receive in tandem a respective auxiliary slide-in unit.

Abstract: A gain control circuit includes a network (112) for splitting a first signal into first and second signal paths with the ratio of the values of the signals in the respective first and second paths being determined in operation by a digital control signal. The circuit includes an input stage (101) the output of which is connected to the input of network (102) so as to provide said first signal, said input stage (101) having a gain which is set by the value of the signal in said first signal path, and an output stage (104) the output of which is controlled by the signal in said second signal path.

Abstract: A Data Switching Arrangement having a plurality of data switching groups connected by a time division multiplexed data highway, each switching group including data interface means having the ability to store segments of data from terminals either prior to transmission in the transmission timeslot or as received from another terminal in the receive timeslot. The timeslots are initially assigned by a central control unit.