Between 1952 and 1954 Fritz Karl Preikschat filed five patent applications for his "teletype writer 7 stylus 35 dot matrix" aka "PKT printer", a dot matrix teletypewriter built between 1954 and 1956 in Germany. Like the earlier Hellschreiber, it still used electromechanical means of coding and decoding, but it used a start-stop method (asynchronous transmission) rather than synchronous transmission for communication. In 1956, while he was employed at Telefonbau und Normalzeit GmbH (TuN, later called Tenovis), the device was introduced to the Deutsche Bundespost (German Post Office), which did not show interest.