Abstract: An acoustic sensor device includes a substrate and a first transducer supported by the substrate, the first transducer configured to generate a first output signal when exposed to a sound wave. The acoustic sensor device also include a second transducer supported by the substrate, the second transducer configured to generate a second output signal when exposed to a sound wave. The first transducer and the second transducer are configured such that the first output signal generated by the first transducer and the second output signal generated by the second transducer are opposite in polarity.

Abstract: A well tool apparatus comprises a control arrangement configured to control response of the downhole tool by varying downhole drilling fluid conditions. The control arrangement includes a valve piston longitudinally slidable in a generally tubular controller housing that is in operation substantially co-axial with the wellbore, to open or close a valve port to a fluid flow connection between the drill strings interior and the tool. A latch mechanism is configured to latch the valve piston in an activated mode and/or a deactivated mode. Unlatching of the valve piston can be effected by displacement thereof in a particular axial direction to a mode change position. A stay member is automatically displaceable in the particular actual direction under hydraulic actuation responsive to above-threshold drilling fluid conditions, to obstruct movement of the valve piston under hydraulic actuation to the mode change position.

Abstract: A well tool apparatus comprises a control arrangement configured to control response of the downhole tool by varying downhole drilling fluid conditions. The control arrangement includes a valve piston longitudinally slidable in a generally tubular controller housing that is in operation substantially co-axial with the wellbore, to open or close a valve port to a fluid flow connection between the drill strings interior and the tool. A latch mechanism is configured to latch the valve piston in an activated mode and/or a deactivated mode. Unlatching of the valve piston can be effected by displacement thereof in a particular axial direction to a mode change position. A stay member is automatically displaceable in the particular actual direction under hydraulic actuation responsive to above-threshold drilling fluid conditions, to obstruct movement of the valve piston under hydraulic actuation to the mode change position.

Abstract: A vacuum cleaner comprises a cyclonic separator (116) for separating dirt and dust from an incoming airflow. A tool (300) and a suction conduit (114) connect the tool (300) to the separator (116). The tool (300) comprises a main air inlet aperture for engaging with a surface to be cleaned and a bleed air inlet (310) for allowing air to bleed into the suction path. The bleed air inlet (310) is located such that it is separate from the main inlet. The cross-sectional area of the bleed air inlet (310) is sufficiently large that, in use, the bleed air inlet (310) admits a sufficient quantity of air to maintain adequate separation efficiency in the separator of the cleaner even when the main air inlet is fully blocked.

Abstract: A guided underwater object (GUO) (100) comprises steering means, an on-board guidance system (200) for controlling the steering means, and a hydrophone unit or units (104A, 104B, 104C, 104D, 104E, 104F, 104G, 104H) arranged to pass signals induced therein by an acoustic guiding beam to the on-board guidance system to effect directional control of the self-propelled underwater object. The GUO is guided by a remote guidance system characterised by a plurality of transmitter arrays (402A, 402B, 402C, 402D; 412A, 412B, 412C, 412D; 422P, 422Q, 422R) arranged to transmit a plurality of contiguous acoustic beams (302A, 302B, 302C, 302D) each having a different frequency or frequency chirp (or other acoustic signal coding) and enclosing a guidance corridor of lower sound level (‘null’) (304) extending approximately in the direction of propagation of the acoustic beams and defining a flight path of the object.

Abstract: A vacuum cleaner comprises a cyclonic separator (116) for separating dirt and dust from an incoming airflow. A tool (300) and a suction conduit (114) connect the tool (300) to the separator (116). The tool (300) comprises a main air inlet aperture for engaging with a surface to be cleaned and a bleed air inlet (310) for allowing air to bleed into the suction path. The bleed air inlet (310) is located such that it is separate from the main inlet. The cross-sectional area of the bleed air inlet (310) is sufficiently large that, in use, the bleed air inlet (310) admits a sufficient quantity of air to maintain adequate separation efficiency in the separator of the cleaner even when the main air inlet is fully blocked.