A method for use in controlling pressure based signal transmission within a fluid in a flowline includes transmitting a pressure based signal through a fluid within a flowline using a flow control device, recognising a condition change associated with the flowline, and then controlling the flow control device in accordance with the condition change. Another method, or an associated method for use in communication within a flowline includes determining or composing an optimised pressure based signal for detection at a remote location and then transmitting the optimised signal using a flow control device.