Abstract: An optical fibre organizer, which comprises:1. first and second ports through which optical fibres can pass;2. an organizer drum positioned with respect to the ports such that a fibre passing between them is constrained by an outer surface of the drum to a minimum bend radius at least equal to the critical bend radius of that fibre;in which the drum is hollow allowing a free end of the fibre to pass from one of the ports to the interior of the drum and to be stored therein at a minimum bend radius greater than at which it suffers permanent damage.

Abstract: An overcurrent protection system which will give a rapid response to relatively small overcurrents. The system, which can be connected between an electrical power supply and an electrical load to form an operating circuit, and which when so connected protects the circuit from overcurrents, has a normal operating condition and a fault condition, and comprises: a circuit interruption element having, (1) a normal state which permits the flow of a normal current, I.sub.NORMAL, when the system is in the normal operating condition, and (2) a fault state which permits the flow of at most a reduced current, substantially less than I.sub.NORMAL, when the system is in the fault condition; and a control element, connected in series with the circuit interruption element, the control element having a variable resistance which (1) is low when the current in the system does not exceed the normal current, I.sub.

Abstract: An overcurrent protection system which will give a rapid response to overcurrents which cause a reduction in the voltage across the load, e.g. a partial or complete short across the load, and is particularly suitable for protecting circuits against relatively small overcurrents, comprising: a circuit interruption element which, in the operating circuit, is connected in series between the electrical power supply and the electrical load, and which has (1) a closed state which permits the flow of a normal current, I.sub.NORMAL, through the circuit interruption element, and (2) an open state which permits the flow of at most a reduced current, substantially less than I.sub.NORMAL, through the circuit interruption element; a control element which, in the operating circuit, is connected in parallel with the load, and which has (1)(i) an on state, when the voltage across the control element is a normal voltage, V.sub.

Abstract: An optical fiber organizer for receiving an optical fiber from one direction and storing loops thereof in a plane substantially perpendicular to that direction, which comprises: a substantially cylindrical block having a port running from an end of the cylinder where it is substantially parallel to the axis of the cylinder to a side of the cylinder such that a fiber within it is directed around the circumference of the cylinder.

Abstract: A maintenance termination unit (MTU) for use in telephone circuits. The MTU comprises a switching arrangement which can be connected between sets of terminal equipment in a communications channel comprising a pair of lines. The switching arrangement comprises: a DC voltage window detector circuit which, in use, is connected between the lines and is responsive to a voltage between the lines; and series switching circuits, which, in use, are connected in the lines. The arrangement may also include a shunt switching circuit, which, in use, is connected between the lines. The arrangement includes low pass filters associated with the switching circuits. The DC voltage window detector circuit will actuate the switching circuits when the DC voltage between the lines is within respective predetermined bands, but will not actuate the switching circuits when the DC voltage between the lines is not within the respective predetermined bands.

Abstract: A maintenance termination unit (MTU) for use in telephone circuits. The MTU comprises a switching arrangement which can be connected in a communications channel, the communications channel comprising a pair of lines. The switching arrangement is connected between a set of exchange-side terminal equipment and a set of subscriber-side terminal equipment. The arrangement comprises first and second line switches, each of which is series connected in one of the lines. Each line switch comprises a control terminal, and has a closed state in which it will pass normal line current, and an open state in which it will pass at most a reduced line current. The arrangement also comprises a control circuit which is connected to the channel between the line switches and the subscriber-side terminal equipment.

Abstract: A circuit protection arrangement comprises a series switching circuit that is intended to be connected in a line of the circuit and will switch to an open state when subjected to an overcurrent, and a shunt switching circuit that is open under normal operating conditions but will shunt the overcurrent across the load of the circuit or to ground when triggered by the series switching circuit. Preferably the series switching circuit comprises a switching transistor (4) that is controlled by a control transistor (6), and the shunt switching circuit comprises a shunt switching transistor (9) that is controlled by a shunt control transistor (11) which is itself controlled by the series switching circuit. The shunt switching circuit may be connected to ground or it may be connected to a back-up load or voltage foldback device such as a triac.

Abstract: A switching arrangement that can be connected in a communications channel comprising a pair of lines, between sets of terminal equipment, which comprises:(i) a pair of series switching circuits, each of which can be series connected in one of the lines and will open when subjected to an overcurrent in its associated line; and/or(ii) one or more shunt switching circuits connected between the lines, or between one or both the lines and earth, and will close when subjected to an overvoltage in its associated line;wherein the or each switching circuit can be remotely actuated by means of a test signal sent along the channel.

Abstract: An arrangement for protecting an electrical circuit such as a telephone circuit from a voltage transient comprises a voltage clamp or foldback device (3) arranged to be connected between a current-carrying line (1) and ground (1'), a capacitor (2) in series with it, and an inductance (4) series connected in the line. During normal operation the arrangement acts as an LC filter whose high frequency break-point is determined by the capacitance of the voltage clamp or foldback device (3) and the value of the inductance (4) which are chosen to give a break point of 1 kHz to 10 MHz. However, when the arrangement is subjected to a voltage transient, the voltage clamp or foldback device (3) fires causing the break-point to fall to a value determined by the values of the capacitor (2) and inductance (4). The arrangement may be used, for example, to protect the circuit against a rapid voltage drop caused by the firing of another circuit protection device such as a gas discharge tube 5.