Abstract: A mud pulser creates pressure pulses in a stream of drilling fluid circulating through a drill string. The pulser has a body connected into the drill string, and defines a flow passage for drilling fluid. A signal poppet having a piston is reciprocally carried within the body. A lower end of the poppet selectively restricts flow of drilling fluid through an orifice and to thereby increase pressure and creates a pulse while in an extended position. An inner passage with an upward facing servo seat formed therein is located in the body and extends through the signal poppet for the passage of drilling fluid. A motor-driven servo valve selectively engages the servo seat to control flow of drilling fluid through the inner passage. A limit switch responds to axial movement of the servo valve cause the motor to turn off when the servo valve reaches predetermined axial positions.