Abstract: A method and apparatus for allowing a transparent service option transition between at least two wireless communication devices (WCDs). A first communication between a first WCD and a second WCD is established using a first service option. At some point during the first communication, a transition to a second service option, such as an asynchronous data service option, is initiated. At least one of the WCDs provides an identification code to the other WCD using a signaling protocol over the first service option. The first communication is then terminated. A second communication using the second service option is then initiated by one of the WCDs, resulting in a seamless transition to the second service option.

Abstract: A digital gas metering system includes inlet and outlet manifolds, a plurality of conduits each extending between the inlet manifold and the outlet manifold, and a solenoid-operated valve in each conduit. At least one of the valves is a tri-stable valve. Each tri-stable valve has a highest flow setting, a lowest flow setting, and an intermediate flow setting. The preferred embodiment utilizes at least two tri-stable valves, and these have respective highest flow settings which form a geometric progression in which each term is substantially triple the preceding term.

Abstract: A tri-stable, solenoid-operated valve defines an internal chamber communicating with an outlet passageway and an inlet passageway, with a valve seat surrounding the outlet passageway. A first piston reciprocates toward and away from the valve seat and supports a closure adapted to close the valve when the first piston is in a first position, and to be spaced away from the valve when the first piston is in a second position. A second piston is mounted to the first piston and can reciprocate toward and away from the valve seat. The second piston has a portion which projects into the outlet causing partial occlusion when the first piston is in its second position and the second piston is in its first position. The portion of the second position causing the outlet to be occluded is substantially withdrawn when both pistons are at their respective second positions.

Abstract: There is disclosed a microscope viewing arrangement adapted for exhibition use comprising a plurality of microscopes, each of said microscope comprising console enclosing a microscope arrangement and affording a common viewing position, remote focussing means operable from the viewing position, and a lamp arrangement adapted to illuminate a specimen position, the focussing means, the lamp arrangement and the specimen position being, in use, inaccessible from the viewing position, and information display means adapted to display information relevant to a specimen mounted in the specimen position and to be changed with such specimen.