Heliographs are devices that use reflected sunlight to send messages or signals, often used in situations where other forms of communication are not possible. Synonyms for heliographs include signal mirrors, sun mirrors, reflective mirrors, and flash mirrors. Other related terms include beacon flashers, sunshine signals, and sun reflectors. In military contexts, heliographs are often called signal lamps or signaling mirrors. Regardless of the term used, all heliographs allow a message to be sent over long distances, making them invaluable tools for communication in remote or dangerous locations where traditional forms of communication are not feasible.