Call centres, and their "agents" sitting with headphones in front of computer screens, have become an important part of British industry.
There are now about 7,000 call centres in Britain.
They employ more than 200,000 people - more than the total number of workers at call centres in the rest of Europe.
Some people refer to call centres as "white collar factories".
Because the work is all done by telephone, they can be located in cheap areas that are often a long way from the company they are serving.
This gives them the great advantage of bringing wealth and employment to run-down areas in far-flung places.
But there is a downside emerging as research is done on this relatively new but important way of working.
Academics from the London School of Economics have studied 250 call centres and found levels of monitoring and control on employees that would have been unimaginable to old factory hands.
It has led critics to dub call centres "new sweatshops" and "battery farms".
One of the researchers, Sue Fernie, writes in the Centre's journal:
"The possibilities for monitoring behaviour and measuring output in call centres are amazing to behold - the 'tyranny of the assembly line' is but a Sunday school picnic compared with the control that management can exercise in computer telephony.
"Indeed, the advertising brochure for a popular call centre software package is titled 'Total Control Made Easy'."
With constant surveillance from the moment they arrive to the moment they leave the office, most telephonists stay in a job for less than two years, according to the research.
"There is a problem of 'burn out': 18 months is usually about as much as a computer telephonist can cope with," says the article.
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London School of Economics - Centre for Economic Performance
Call Centre focus
Call Centre Organisation - professional body
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