Some 8th AF bombers were equipped with SCS-51 receivers. Sometimes the SCS-51 vertical localiser transmitters and 2 marker beacons were placed near the us frontline to prevent bombing own troops. Like during operation Queen, 1st and 9th armies near the Roer river, Nov. 16th 1944. The bombardiers used the markers beacons to stay on course and the localiser beacon to release the bombs. 1204 heavies bombers attack Eschweiler and Langerwehe. In some cases their was a us ground control station, near the target, that kept radio contact with the bombers.