Pantelegraph

The pantelegraph (Italian: pantelegrafo; French: pantélégraphe) was an early form of facsimile machine transmitting over normal telegraph lines developed by Giovanni Caselli, used commercially in the 1860s, that was the first such device to enter practical service, It could transmit handwriting, signatures, or drawings within an area of up to 150 × 100 mm.

The pantelegraph used a regulating clock with a pendulum which made and broke the current for magnetizing its regulators, and ensured that the transmitter's scanning stylus and the receiver's writing stylus remained in step. To provide a time base, a large pendulum was used weighing 8 kg (18 lb), mounted on a frame 2 m (6 ft 7 in) high. Two messages were written with insulating ink on two fixed metal plates; one plate was scanned as the pendulum moved to the right and the other as the pendulum moved to the left, so that two messages could be transmitted per cycle. The receiving apparatus reproduced the transmitted image by means of paper impregnated with potassium ferricyanide, which darkened when an electric current passed through it from the synchronized stylus. In operation the Pantelegraph was relatively slow; a sheet of paper 111 mm × 27 mm, with about 25 handwritten words, took 108 seconds to transmit.

The most common use of the Pantelegraph was for signature verification in banking transactions.

While employed teaching physics at the University of Florence, Giovanni Caselli devoted much time to research into the telegraphic transmission of images. The major problem of the time was to get perfect synchronization between the transmitting and receiving parts so they would work together correctly. Caselli developed an electrochemical technology with a "synchronizing apparatus" (regulating clock) to make the sending and receiving mechanisms work together that was far superior to any technology Bain or Bakewell had.

By 1856, he had made sufficient progress for Leopold II, Grand Duke of Tuscany to take an interest in his work, and the following year he travelled to Paris where he was assisted by the engineer Paul Gustave Froment, to whom he had been recommended by Léon Foucault, to construct the first Pantelegraph. In 1858, Caselli's improved version was demonstrated by French physicist Alexandre-Edmond Becquerel at the French Academy of Sciences in Paris.

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