by positive mud pulses using a flow restricting valve within the drill pipe

Survey of boreholes or wells > Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling > using acoustic waves > through the well fluid > by positive mud pulses using a flow restricting valve within the drill pipe

Survey of boreholes or wells (monitoring pressure or flow of drilling fluid E21B21/08) > Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling > using acoustic waves > through the well fluid > by positive mud pulses using a flow restricting valve within the drill pipe