Fax is short for Facsimile - the ability to send an image (a replica of a piece of paper) - down a line. It seems like a sophisticated telecommunications technology and people think of it as quite recent - an invention of the 1970s or 1980s.
In fact, it's one of the oldest - an offshoot of the chemical telegraph invented by Alexander Bain in 1843. The reason fax took such a long time to develop is that the machinery to use the technology wasn't really there at first. So the experience of actually sending or receiving a fax has changed most radically of all.
Originally fax machines were large, heavy and very expensive. Their use was confined to newspaper offices and weather stations and other specialised users, with wet chemicals for developing the images received.
What transformed the fax was the advent of printers that produced pictures without messing processing or delay. Manufacturers could now transform the fax machine into a convenient piece of office, and later consumer, electronics. By 1980 the bulk had been reduced to the size of a laser printer but use of the fax was still limited.
In Britain, the turning point came with a number of lengthy postal strikes - suddenly a broader application for fax machines was clear.
In the early 1990s Amstrad, BT and other suppliers brought out compact models for small business and home use, still relying on rolls of coated paper. When the thermal system was replaced by inkjet machines, printing onto plain A4 paper the user-friendly fax machine finally arrived.
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Like the telephone, the facsimile (or 'fax') machine was also developed as an offshoot of the telegraph.
This too developed into a communications technology in its own right - with a long delayed 'take off' that owed its success to accidents of history.
When Alexander Bain developed his chemical telegraph in 1843, he intended a device that could be used to draw letters - and then trace their outlines one at a time at the other end.
What Bain failed to see is that if you could do that then you could transmit whole images - including pages of text line by line. But to make that a reality required new technology that was borrowed from computer printers - with the Japanese first to see how the two could be combined in the late 1970s.
Under their touch, the fax became truly useful and affordable.
