The synchronization of the devices is carried out manually, at the beginning of the transmission, making it possible to send images through the telegraph cables. Caselli got to work in 1857, and for six years perfected something he called the pantelegraph, the world’s first fax machine. Measuring 1.8 meters high and made of batteries, wires and swinging pendulums, it worked by passing an electric current through an image. The signal was sent to a receiver that translated it onto a sheet of treated paper.
On the transmitting side, a needle connected to a pendulum swung over the original document. When it touched the ink, it sent an electrical signal to a synchronized needle that passed over chemically treated paper on the other side. This caused the paper to change color every time the electricity touched it. The result was an exact copy.