Sign language is just radio communication but on another frequency
Because you use light to communicate in sign language, and light is just an electromagnetic wave like radio but on another frequency. You just need to be in line of sight
Really, radio communication is about creating and transmitting those radio waves. Sign language relies on reflected light waves so it’s actually a form of RADAR 😀
That’s just what the acronym means, it doesn’t describes the actual process. I don’t think there is a single RADAR that doesn’t have a transmitter. At that point it would just be a… radio.
Fair enough, though I would argue that’s a very specific subtype of radar and anyone saying “radar” refers to the type that is used in 99.999% of the cases.