Abstract: Information is conveyed from a downhole location within a wellbore being drilled by producing pressure and velocity of flow variations from the steady state drilling fluid pressure and velocity of flow so as to set up transient acoustic waves that propagate to the surface through the drilling fluid within the drill string. The acoustic waves are detected at the surface to obtain the propagated information. According to this invention, a simple and reliable method of recovering the propagated information is to monitor the pressure of the gas filled side of the accumulator or desurger device that is coupled to the drilling fluid line adjacent the pump.