Kurier was a burst transmission system for U-boat communications that was first sea trialed by the Kriegsmarine in 1943[1] and subsequently fitted to the Type XXI submarine.[2]: 103–104 Having learned of the success of the UK's "huff-duff" systems in rapidly locating radio transmissions, Kurier was developed to dramatically reduce message transmission times from a typical 20 seconds to about 250 ms, and never longer than 450 ms (just under ½ a second). Due to the deteriorating position of Germany by that time, Kurier never became operationally effective before the war ended.