Article discusses a research about communication system intended to warn people in danger. This system aims to distribute a voice message with pre-recorded content to inform participants about the target events in their area using Voice over IP technology. Transmission of information via voice messages has, compared with other ways of message distribution, the advantage that the target user is forced to pick up the call and listen to the message—and therefore the information cannot be ignored or overlooked. Another advantage is more accurate addressing of target groups of subscribers and, last but not least, it is possible to ensure the re-delivery of messages to users who did not receive a call.Web of Science851766