 However, it also caused problems for the Germans, as it sometimes detected stray radar emissions from distant ships or planes, causing U-boats to submerge when they were not in actual danger, preventing them from recharging batteries or using their surfaced speed.Metox provided the U-boat commander with an advantage that had not been anticipated by the British.The Metox set beeped at the pulse rate of the hunting aircraft's radar, approximately once per second.