Very early experimental printing telegraph devices used only a start bit and required manual adjustment of the receiver mechanism speed to reliably decode characters. Automatic synchronization was required to keep the transmitting and receiving units "in step". This was finally achieved by Howard Krum, who patented the start-stop method of synchronization (US 1199011 , granted September 19, 1916, then US 1286351 , granted December 3, 1918).