heliograph
/ˈhiːliəˌɡræf/
verb
- To send a message using a heliograph.
- The scouts learned how to heliograph across the desert.
- We heliographed our position to the rescue team.
- They heliographed the warning to the next outpost.
noun
- A device that uses mirrors to reflect sunlight and send signals (like Morse code) over long distances, used especially in the past for military communication.
- The soldiers used a heliograph to send a message across the valley.
- Before radios, the heliograph was a key tool for long-distance communication.
- We saw a heliograph flashing on the distant hilltop.
- A photograph taken by sunlight, especially an early type of photographic image.
- The museum displayed a heliograph from the 1820s.
- Early heliographs required hours of exposure in bright sunlight.
- He studied the faded heliograph of the old city square.