I acquired this Signal Corps Keyer TG-34-A about five or six years ago.  It uses a paper tape encoded with a signal line that looks similar to a square wave.  Looking at the tape the dots and dashes of the encoded Morse code are plainly visible.  The last pictue is a composite of the 2nd and 3rd photos with the english letters of the Morse code encodings printed underneath them.

This is a Vintage 1943 Signal Corps Keyer Model TG-34-A.  The brass label it reads "Signal Corps Keyer TG 34 A 115/230 Volt, 50-60 Cycle AC, 5656 CZJ, 21841-Phila- 43."

This Keyer which was made to last and features a heavy duty wood and metal military case unlike anything made today.  It measures 10"x10.5"x15" and weighs 44 pounds.