You will want to practice so you can record and play back at the same speed. When recording, speak in a very loud and clear voice into the horn. Playback After recording, back the RR needle away from the foil. Rewind the cylinder to its original position. You should hear what was recorded through the horn.
Adjustments are critical, since the foil can be torn or the recording erased very easily.
It will take much trial and error to use it expertly. We made it work after many difficulties. And the needle needs to be adjusted carefully so that it makes a groove in the foil while recording without tearing the foil. It should contact the foil somewhat lighter when reproducing the sound. You will only get this right by much trial and error.