A little history

Bain's pendulums, 1843

The fax is older than the telephone. In 1843 the Scottish clockmaker Alexander Bain patented an “electric printing telegraph”. At the two ends of the line two pendulums swung, and clocks kept them in step. The transmitter's pendulum moved a needle over metal letters: when the needle touched metal, current went down the line. The receiver's pendulum moved its own needle over paper soaked in a solution that darkens from the current. After each swing the sheet moved on by one line. Line by line, dot by dot — ours does the same, only the pendulum has been replaced by a carriage on a belt.

transmitterclockBAINmetal typereceiverclockpaper darkens with currentline: current — no currentthe pendulums swing in step
Bain’s telegraph (1843): the transmitter needle passes over the letters, the receiver needle over chemical paper; after each swing the sheet moves one line. The copy is made of stripes — line by line.

Caselli's pantelegraph, 1865

The Italian priest and physicist Giovanni Caselli built the pantelegraph — a machine as tall as a person, with a pendulum more than two metres long. In 1865 the world's first picture transmission service opened between Paris and Lyon: signatures, technical drawings, pictures. The main difficulty was the same as ours in lesson 7: the receiver must draw a line in the same second as the transmitter reads it. Caselli kept the pendulums in step with clocks. In ours every line begins with a start bit — the receiver starts the line from it and cannot fall behind by more than one line.

The drum and the photocell, 1900–1930

The sheet came to be wrapped around a drum: the drum turns, and a head with a photocell slowly creeps along it — this gives a spiral of lines. The German physicist Arthur Korn sent photographs this way in the 1900s, and in 1913 the Frenchman Édouard Belin made the portable “Belinograph” — with it reporters sent pictures to their newspaper right from the scene. Before starting, the machines listened to phasing pulses: the receiver's drum adjusted itself so that the start of the line matched.

A fax in every office, 1966–1980

In 1966 the Xerox company released the Magnafax Telecopier: 21 kilograms, an ordinary telephone line, six minutes per page. In 1980 the international communications committee approved the Group 3 standard: a sheet goes in a minute, a line is 1728 dots. The standard has two modes: “standard” — 3.85 lines per millimetre, and “Fine” — twice as often, 7.7. Our fax also has a FINE switch: the sheet is fed by a line not in two steps, but in one.

Group 3, standard8 lines in 2 mmGroup 3, Fine15 lines in 2 mmour fax, lesson 72 lines in 10 mmour fax, lesson 88 lines in 10 mm
Line pitch: Group 3 standard — 3.85 lines per millimetre, Fine — 7.7. Our fax: a 5.2 mm line in lesson 7, 1.3 mm with FINE in lesson 8. The first two squares are 2 mm, the other two 10 mm.

Needles and thermal paper

Receiving machines printed in different ways: with a spark on special paper, with needles, and the most common ones with heat: a thermal head across the sheet and paper that darkens from heat. Dot-matrix printers struck a dot with a needle through an inked ribbon. Our pen in lesson 9 also becomes a needle: it goes down only while the carriage is standing still — every dot exactly in its place.