Notification devices are audio and/or visual devices used to notify occupants and/or responders of various alarm conditions. On average horn/strobes are installed at 90 inches height and if ceiling is less than that then you install at 6 inches below ceiling. The outside strobe or horn/strobe should be installed in a fire dept approved location. Also some fire depts have special requirements regarding notification devices, so please be sure to check with them before installing any of these devices.