Signal (2016-) 
Detectives from the present and a detective from the past communicate via walkie-talkie to solve a long-time unsolved case.
Signal: Season 1 Season 1 (Full Season)
Detectives from the present and a detective from the past communicate via walkie-talkie to solve a long-time unsolved case. (Netflix, tvN Korea) [more inside]
Signal: Episode 1 Season 1, Episode 1
Profiler Park Hae-young hears a man calling his name through a discarded two-way radio. The voice starts talking about an unsolved crime. (Korean drama, Netflix) [more inside]