The hailer on VHF marine radios are a type of PA system. Using a loud speaker connected to the input hailer jack on the radio, it can be used like a PA system. This really works well with a helm station inside and crew working on deck, as they can hear you without leaving the cabin. It is also used from vessel to vessel in close communications, over water or boat to shore. Remember though that you cannot hear from this loudspeaker, only amplifies your voice. Other types of speakers can incorporate both hearing and voice through some hailers. It depends on the brand.
