In terms of video games, to telegraph is to give advance notice of. A good example is Punch Out. Most fighters do a small animation that shows they are about to attack.
A song from Schoolhouse Rock, which depicts a Civil War-esque delivery boy sending messages and death threats to various people in the song. Telegraph Line is also famously known for having a robot with a lit-up screen being sexually abused by Mr. Hand, mainly in the areas of the foot.
Hey, there's a telegraph line, you got yours and I got mine; it's called the nervous system!!!!!!!!!!!!! And everybody understands, those telegram commands, and you know that everybody better listen!