He was knighted for developing the heliograph. The first digitally controlled heliograph was designed and built in 2015. It also had a powerful electric searchlight with a heliograph shutter. The designer described the Solar Beacon as a "heliostat", not a "heliograph". Obsolete names for Sun telescopes include heliograph and photoheliograph. In open warfare, visual signalling (employing signal flags and the heliograph) was the norm. It has also been called a heliograph. Another type of heliograph was the heliostat fitted with a Colomb shutter. However, there is little evidence that "heliograph" here is other than a misspelling of "holograph". The U. S. Signal Corps heliograph mirror did not tilt. The heliograph is a telegraph system using reflected sunlight for signalling. The term "heliostat" is sometimes used as a synonym for "heliograph" because of this origin. The heliograph was standard military equipment as late as World War II. The heliograph uses a mirror to reflect sunlight to a distant observer. In good conditions, the heliograph could transmit over distances as great as 50 miles.