▁transmission ▁duration ▁of ▁messages . ▁ ▁Description ▁ ▁The ▁transmission ▁of ▁radio ▁messages ▁had ▁the ▁potential ▁ris ks ▁of ▁reve aling ▁the ▁sub marine ' s ▁presence ▁and ▁direction ; ▁if ▁dec oded ▁the ▁content ▁was ▁also ▁revealed . ▁Sub mar ines ▁need ▁to ▁provide ▁information , ▁mostly ▁in ▁standard ▁form ▁( position ▁of ▁con voy ▁to ▁attack ▁and ▁of ▁sub marine , ▁weather ▁information ), ▁to ▁their ▁bases . ▁Initial ly ▁Mor se ▁code ▁transm issions ▁could ▁be ▁used . ▁To ▁in hib it ▁detection , ▁the ▁duration ▁of ▁messages ▁needed ▁to ▁be ▁minim ised ; ▁for ▁this , ▁Kurz sign ale ▁short - c oding ▁was ▁used . ▁To ▁prevent ▁inter ception , ▁messages ▁needed ▁to ▁be ▁encrypted ▁by ▁the ▁En igma ▁machine . ▁To ▁short en ▁transmission ▁even ▁further , ▁the ▁message ▁could ▁be ▁sent ▁by ▁a ▁fast ▁machine ▁instead ▁of ▁a ▁human ▁radio ▁operator . ▁For ▁example , ▁the ▁Kur ier ▁system ▁– ▁not ▁implemented ▁in ▁time ▁– ▁decre ased ▁the ▁time ▁to ▁send ▁a ▁Mor se ▁dot ▁from ▁around ▁ 5 0   mill iseconds ▁for ▁a ▁human ▁to ▁ 1   mill isecond . ▁ ▁Short ▁Sign al ▁book ▁The ▁Kurz sign ale ▁code ▁was ▁intended ▁to ▁short en ▁transmission ▁time ▁to ▁below ▁the ▁time ▁required ▁to ▁get ▁a ▁direction al ▁fix . ▁It ▁was ▁not ▁primarily ▁intended ▁to ▁hide ▁signal ▁contents ; ▁protection ▁was ▁intended ▁to ▁be ▁achieved ▁by ▁encoding ▁with ▁the ▁En igma ▁machine . ▁A ▁copy ▁of ▁the ▁Kurz sign ale ▁code ▁book ▁was