In order to track a raptor who has flown away, many falconer use radio telemetry. Typically a transmitter is temporarily attached to the leg at the jess or on a bewit. Sometimes a mount for it may be attached to one of the center tail feathers by very careful application of a small drop of Superglue. Recently, a lightweight harness made of Teflon tape has also been employed as a means of hanging the transmitter off the middle of the bird's back (out of the way of the bird's flight and footing, so as to minimize interference with the hunt.) The transmitter emits a radio Beep, which the falconer can track with a portable receiver. By listening to how the signal gains or loses strength a practised person can gauge if the bird is sitting still, if it is flying, and what direction it is going in. Practice with telemetry is very important, as there is no time for learning when a falcon is flying away!