Pantelegraph

Lore & Background

While teaching physics at the University of Florence, Giovanni Caselli researched the telegraphic transmission of images. The major problem was achieving perfect synchronization between transmitter and receiver. Caselli developed an electrochemical technology with a 'synchronizing apparatus' (regulating clock) far superior to earlier technologies by Bain or Bakewell. By 1856, his progress attracted the interest of Leopold II, Grand Duke of Tuscany. The following year, Caselli traveled to Paris, where engineer Paul-Gustave Froment, recommended by Léon Foucault, helped construct the first pantelegraph. In 1858, an improved version was demonstrated by physicist Alexandre-Edmond Becquerel at the French Academy of Sciences. On 10 May 1860, Napoleon III visited Froment's workshop, was enthused by the device, and secured access to telegraph lines from Froment's workshops to the Paris Observatory. In November 1860, a line between Paris and Amiens enabled a successful long-distance experiment over 140 km, transmitting the signature of composer Gioacchino Rossini. Rossini wrote a piano piece, allegretto ‘del pantelegrafo’, to mark the event.

Reader's Guide

The pantelegraph used a regulating clock with a pendulum that made and broke the current for magnetizing its regulators, ensuring the scanning and writing styli remained in step. Two messages were written with insulating ink on fixed metal plates; one plate was scanned as the pendulum moved right, the other as it moved left, allowing two messages per cycle. The receiver reproduced images on paper impregnated with potassium ferricyanide, which darkened when current passed through it from the synchronized stylus. Operation was relatively slow: a sheet of paper 111 with about 25 handwritten words took 108 seconds to transmit. The first 'pantelegram' was sent from Lyon to Paris on 10 February 1862. The Corps législatif ordered installation on the railway line between the two cities, and from February 1863 the public could use it. French law enacted in 1864 officially accepted the system. Operations on the Paris–Lyon line began in 1865 and extended to Marseille in 1867. Russian Tsar Alexander II installed an experimental service between his palaces in Saint Petersburg and Moscow from 1864 to 1865. In 1867, a second line from Lyon to Marseille was set up; transmission cost was 20 centimes per square centimeter of image, and the service operated until 1870.

Did You Know?

• The pantelegraph could transmit handwriting, signatures, or drawings within an area of up to 150.
• The composer Gioacchino Rossini wrote a piano piece, allegretto ‘del pantelegrafo’, to mark the first long-distance transmission.
• The most common use of the pantelegraph was for signature verification in banking transactions.