Abstract: The present invention provides a gun brake system adapted to slow the descent of a tool string in a well. In one embodiment, the brake system comprises a brake installed within the well and having a snug fitting restriction and one or more fluid channels extending along a portion thereof. The brake system further provides means for maintaining the fluid volume substantially constant within the production tubing to which the gun brake is installed.

Abstract: The present invention provides a gun brake system adapted to slow the descent of a tool string in a well. In one embodiment, the brake system comprises a brake installed within the well and having a snug fitting restriction and one or more fluid channels extending along a portion thereof. The brake system further provides means for maintaining the fluid volume substantially constant within the production tubing to which the gun brake is installed.

Abstract: A multi-level quadrature (I/Q) mixer for use in a communication system such as a paging device, where the mixer includes first and second I/Q downconversions followed by demodulation. The first I/Q downconversion converts an I/Q signal pair to a first IF, and the second I/Q downconversion converts an I/Q signal pair to a second IF. The first IF may or may not be the center frequency depending on the number of subchannels in the single channel being downconverted.

Abstract: Each section (1) of a drill pipe string carries a substantially annular protector (2) that is movable in a freely rotatable manner around (4) the longitudinal axis of the section (1) concerned. Each protector (2) is also movable lengthwise (3) throughout the length of the section (1) between junctions at its opposite ends or to an extent that is limited by retaining rings secured in appropriate positions around the section (1). Each protector (2) is formed from a relatively hard material having a very low co-efficient of friction, such as polytetrafluoroethylene, and is advantageously produced in two separable halves (FIG. 3) to facilitate embracing assembly around, or quick removal from, the co-operating pipe section (1). If necessary, the protectors (2) may be formed throughout their axial thicknesses with flutes significantly to reduce the fluid flow constraint produced by the presence of the protectors (2).