Technology doesn't have to be new to be interesting. Taking a peek into the past can help us learn how things work and why they are the way they are. We also have the advantage of modern fabrication technologies to help us re-invent the technology of the past. Instructables user Mattox did just this with a 3d printed key and sounder.
This is a complete telegraph system – including both the key and sounder device, ready to be printed. It was designed in Tinkercad, and was printed on a Dremel 3D20 printer. There are some modern improvements, such as using neodymium magnets, instead of springs, to hold up the key and sounder arm. The sounder also uses a MOSFET to improve the sensitivity and reliability of the key. It can even record telegraph messages on a strip of paper with a marker. I am showing this retro-tech to my students as a part of an electricity unit where students can test their ‘texting’ capabilities old-school.