Abstract: This system provides a warning or alert to persons in vehicles of the presence of emergency vehicles which are emitting audio warning signals. The system converts audio signals to discrete signals, which are also frequency indicative, and then determines whether the discrete frequency indicative signals represent warning signal frequencies. The system also determines whether any warning signal is of sufficient duration to be valid, and if they are, activates the warning device in the vehicle. The warning device may alert the vehicle occupants of emergency vehicles in the vicinity by either audio or visual alarms, or by both.