The above instruments were to stabilize the plane, to keep it to an even keel in flight mostly. Now came an instrument to help at landing--the visual radio receiver. This consisted of two little vibrating reeds tuned to the radio beacons in use in landing fields. If, in aiming at a landing, Hal turned to the right of his course, the right reed vibrated, while at too much of a left turn, the left reed registered its little movement. So by keeping the two reeds in a balancing quiver, he could fly directly down the path of the beacon to a landing.