Pantograph but you are correct that's how they work. I had one. It took two hands one to trace in the letters or patterns and the other to press the head down to the work. Great tool to have. I used mine to engrave a few one off dials and they came out great.Today I'm sure it's CNC. When I was a machinist, we had this router called a Kantograph that was attached to the work or a fixture. You put letter patterns in a holder and then traced them onto the work by running a stylus through the slots in the patterns (and I believe I remember having to hold the router head down on the work).