1/2 Sunday DX Headlines will experiment with Slow Hell at 144 Hz. Another invention from before WW2. Hellschreiber was invented in Germany by Rudolf Hell in the late 1920's. It came into use in the early 1930's. Because it doesn't have a fixed character set, it rather transmits small images for each character, the system also gained some popularity in Asia.
Social media for Slow Scan Radio and the Daily Minutes