Electronics Engineering · CHAPTER 01 · FOCUSED LESSON
The first practical machine to transmit handwriting and drawings over wires.
The Pantelegraph scanned conductive and insulating marks at the transmitter and reproduced them electrochemically at a synchronized receiver.
Abbé Giovanni Caselli's machine could send still images of roughly 15 × 10 cm over an ordinary telegraph connection. Unlike an experimental curiosity, it entered practical service during the 1860s and became an early working ancestor of the fax machine.
The information was not photographed and sent all at once. It was converted into a sequence of electrical contact states as a stylus scanned across the original.
A regulating clock repeatedly magnetized the control mechanisms so that the transmitting stylus and receiving stylus remained in step. The large pendulum weighed about 8 kg and stood in a frame roughly 2 m high.
Two messages could be written in insulating ink on two fixed metal plates. One was scanned as the pendulum travelled right and the other as it travelled left, allowing two transmissions per full cycle.
At the receiver, the synchronized stylus moved across paper impregnated with potassium ferricyanide. Where current passed, the paper darkened and recreated the transmitted marks line by line.
The process was slow but real: Ali's document reports that a strip measuring 111 × 27 mm and containing about 25 handwritten words required 108 seconds. The machine demonstrates the three foundations of image transmission—scanning, synchronization and recording.
THE IDEA TO REMEMBERThe Pantelegraph converted a two-dimensional image into a timed electrical sequence and reversed the process at the receiver.
TIME BASE
8 kg synchronized pendulumRECORDING
Potassium-ferricyanide paperEXAMPLE SPEED
25 words in 108 secondsCOURSE SOURCE · “ELECTRONICS AND TECHNOLOGY” · ALI CHOURBA