Did anyone else notice how the Security Forces/Police were using whistles to signal each other during the chase scene of the bad guy gunman after he assasinated the elderly scholar? Does anyone know anything about that? Were whistles actually used in the Joseon era like that? And if so, does anyone know where I can read more about it? Like the type of whistles, how they were made and used. I tried google search several times but never got any results that were even close. I just think it's a neat idea for close-in signaling, as whistles sound carries a long way, and a planned out set of signals-if changed on a regular basis, to keep the opposing forces from learning them, is a good idea. I'm doing research for a story.