A downhole tool for generating a fluid pressure pulse, and to a method of
generating a fluid pressure pulse downhole. One example being, an
improved downhole tool and method for transmitting data signals from a
downhole environment to surface, the downhole tool comprising a fluid
actuated flow restrictor; a first fluid flow path for flow of actuating
fluid to actuate the flow restrictor; a second fluid flow path for flow
of actuating fluid to actuate the flow restrictor; and a control member
movable between a first closed position where the first fluid flow path
is closed and the second fluid flow path is open, and a discrete second
closed position where the first fluid flow path is open and the second
fluid flow path is closed, for controlling actuation of the flow
restrictor to generate a fluid pressure pulse.