#visual_signal  a signal that involves visual communication
  supertype:  signal__sign__signaling  any communication that encodes a message; "signals from the boat suddenly stopped"
  subtype:  watch_fire  light.visual_signal  warning_light  flare  signal_flag  windsock  post.visual_signal  turn_signal  armband.visual_signal  rocket.visual_signal  beacon_fire  stoplight  barber's_pole
  part of:  visual_communication  communication that relies on vision

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