Null By Morse is an installation artwork that incorporates a military signaling lamp and smartphones. A series of Morse messages is transmitted automatically by the signal lamp. The messages are drawn from the history of Morse and telegraphy. A custom app for iPhone and Android uses the phone's camera to identify the changing light levels of the lamp and the associated timings. The app then decodes the Morse and displays the message on the screen on top of the camera image. This paper discusses the artwork in relation to the following theoretical aspects: It contextualizes the position of smartphones in the history of optical communication. It proposes an approach to smartphones in media art that moves away from futurist perspectives whose fundamental approach is to seek to creatively exploit the latest features. Lastly, it discusses the interaction with the phone in the exhibition context in terms of slow technology.