The term "xerography," the use of photoelectric phenomena to transfer an image from one sheet of paper to another, comes from the Greek words for "dry" and "writing." Chester F. Carlson, a New York City patent attorney who had studied chemistry at the California Institute of Technology, first demonstrated this technique. You can say the birth of xerography occurred on October 22, 1938, in Astoria, Queens, N.Y., when Carlson used the process to print this notation on a glass slide using India ink.
In 1944 Battelle Memorial Institute, a nonprofit research organization, entered into a royalty-sharing arrangement with Carlson. Battelle eventually signed a development contract in 1947 with Haloid Company, a Rochester, N.Y., firm that produced photographic paper and later became Xerox Corporation. The first xerographic machine came onto the market in 1949, but it was slow, dirty and hard to use. Not until 1959 did Xerox introduce an office copier, the 914, which became the basis for the current multibillion-dollar industry.
It is always very difficult to relate an invention with a specific date. For example in this case you could argue that 1938, the birth of xerography is actually more relevant. But I think in the context of focussing on the social implications it makes more sense to mention the start of practical usage.
Until this date it was hard to get a pretty exact copy of written text without producing a transcript. It also had effects on the publishing industry. And when we think about the publishing industry today in the digital age we can probably learn something from the days of inventing the photocopier.
Related webaddresses:
http://www.yesterdaysoffice.com/index.cfm?fuseaction=ShowArticle&articleid=26
http://users.pipeline.com.au/mma/pages/History/copier.htm
http://www.intown.com.au/pages/lifestyle/techno/techno_history/copier.htm
http://palimpsest.stanford.edu/bytopic/repro/nadeau1.html
http://news2.thls.bbc.co.uk/hi/english/sci/tech/newsid%5F198000/198264.stm
This technology has already been used for years in certain military applications, and for medical uses, such as therapy for victims of stroke and other brain injuries. It has also been used for the rehabilitation of criminals. The electrical stimulation increases brain 'plasticity', enabling it to adapt more quickly to new learning or behavior, than might otherwise be the case.
Source: http://kurellian.tripod.com/s2049.html#section6.5