a vortex chamber fluid pulser selectively produces pressure pulses in fluid flowing therethrough by the alternating insertion and retraction of a flow - disrupting tab into and out of an annular vortex chamber having an inlet and a pair of opposed axial outlets . insertion of the tab disrupts the normally radial flow of fluid through the chamber and outlets causing the flow to become vortical ; retraction of the tab causes a second pressure pulse as the flow returns to radial , sending a sequence of pressure pulses capable of carrying encoded signals to a transducer remotely located in the fluid .