In the world of tech news, there are certain number of players that dominate the headlines. Apple! Microsoft! Dell! Oracle! IBM! Facebook! And yet \n\nthe world of the tech business is much deeper than this, and there are many companies that employ thousands and make billions and yet don't have \n\nmuch of a profile among even the tech-savvy observers. This article doesn't pretend to offer a comprehensive list of such corporations, but the six \n\ncompanies profiled here do serve as a stand-in for the kind of below-the-radar firms that any tech observer should know more about. They aren't \n\nconsumer focused; they aren't flashy or led by charismatic visionaries; they sell to people who sell to people who sell to you; and the modern world \n\nwouldn't work right without them. Pictured: You've almost certainly come into contact with code written at this Tata Consultancy office in Hyderabad, \n\nIndia.\n\n\nFlextronicsFor most electronic equipment, the brand on the device is not necessarily the name of the company that owns the factory where it was put \n\ntogether. Singapore-based Flextronics is a good example. You don't own anything with a "Flextronics" label on it, but the company made $24.1 \n\nbillion in revenue off of any number of gadgets that probably lurk in your house. They have a hand in building inkjets for HP; phones for Motorola, RIM and Sony Ericsson; power supplies for Dell PCs and hard drives \n\nfor Western Digital. They made it possible for software giant Microsoft to put out hardware like the Zune and the XBox, and they were intimately enough involved in the iPad manufacturing supply chain that one of their directors was able to \n\nsell insider secrets about Apple's plans to hedge funds. They probably didn't make your toilet or your breakfast cereal, but you can't be too sure. Pictured: \n\nFlextronics execs pose with Mexican President Felipe Calder\u00f3n. Mexico is one of 30 countries where Flextronics maintains a manufacturing \n\npresence.\n\n\nCenturyLinkEver since the U.S. government broke up AT&T's telecom monopoly, the company has been reassembling itself, like bits of liquid metal coming \n\ntogether to reform the T-1000 in "Terminator 2." Much of the country's local landline service is now provided by a reconstituted AT&T, while in the \n\nNortheast that role is filled by Verizon. It's easy to forget about Qwest, formerly US West, which takes the Rockies as its territory. But even people \n\nwho can smugly name all the Baby Bells (remember Nynex? Good times!) may not know that, while the Qwest brand name survives in many markets, \n\nit no longer exists as an independent company. In April 2010, it was acquired by CenturyTel, which was descended from a tiny Louisiana local \n\nexchange. Qwest was only the last of a series of telecom companies it had swallowed up over the years; now calling itself CenturyLink, it's the third-\n\nlargest telecommunications company in the country. CenturyLink has over $7 billion in annual revenue, and is still based in Louisiana. Pictured: \n\nMonroe, La., now has its own little chunk of Ma Bell's corpse.\n\nEquinixEquinix has littered the landscape with dozens of low-key data centers, colocation \n\nfacilities and "Equinix Internet exchanges." The latter route traffic among more than 600 different telecom providers from all over the world; Peter Van \n\nCamp, the company's executive chairman, calls them "international airports where \n\npassengers from many different airlines make connections to get to their final destinations." The company's also in the cloud business and provides direct access to AWS. Altogether, something like 90% of all Internet traffic passes through Equinix's hands in one way or \n\nanother, which is unnerving considering "Equinix" sounds like nothing so much as a sinister company from a mid-1990s sci-fi story set in a \n\ncorporate-ruled future dystopia. Equinix reported nearly $900 million in revenue and more than 1,900 employees in 2009. Pictured: Who even knows \n\nwhat's happening inside this mysterious data center?\n\n\nCrown Castle InternationalWireless connectivity might seem like a ubiquitous and intangible product, but it doesn't happen without thousands of tall metal structures \n\nfestooned with electronics and radio transmitter. The famous companies whose names are plastered all over your credit card bill in many cases can't \n\nbe bothered with this kind of nuts and bolts stuff, so they turn to infrastructure companies like Crown Castle International. Crown Castle is based in the U.S. and supplies the wireless backbone in 68 of the 100 largest U.S. cities; \n\nelsewhere its even more omnipresent, reaching 92% of Australian customers. Your cellphone carrier would like you to blame them when you drop a \n\ncall. Pictured: This rural eyesore provides delicious mobile connectivity to rural Britain, courtesy of Crown Castle.\n\n\nScience Applications International Corporation\nSelling computers, software and services to individuals or even companies can be something of a chore, because eventually there's not enough \n\nmoney to buy even the most coveted stuff. But over the last 10 years, the various U.S. defense, law enforcement and intelligence agencies have \n\nbeen eager to spend on high tech -- which explains Science Applications International Corporation's $10 billion in 2009 revenues. SAIC makes \n\nmoney on perfectly normal projects, like modernizing various Army systems. But then there are the weird ones, like the Stargate Project, which sought to harness psychic phenomena for military \n\npurposes. Or the mysterious ones, like the Trailblazer Project, a vast \n\nNSA data-mining operation that was eventually killed after a number of whistleblowers revealed dubious spending and purposes. Or just plain failed \n\nones, like the Virtual Case File program for the FBI that cost $170 million \n\nand was abandoned unfinished. Pictured: We assume no more crackpot and\/or money-wasting projects are going on behind those mirrored \n\nwindows.\n\nTata Consultancy ServicesThe Tata Group is a sprawling business empire, one of India's largest, oldest and most storied companies. Tata Consultancy Services began as an \n\nin-house computer services division, but quickly started taking in clients from other companies, then other countries. Today it has more than \n\n200,000 employees -- many of whom are doing the sorts of things you expect out of an Indian outsourcing firm, toiling on software projects for big \n\ncompanies in the West: two recent clients include CUA, a \n\nmajor Australian credit union, and Air Liquide, which provides services to natural gas distributors (see how these "services" firms form staggering \n\nworldwide chains of outsourcing?). Much of the code that runs behind the websites and businesses you interact with has been built by Tata. \n\nPictured: Tata Consultancy Services CEO N. Chandrasekaran.\nRead Josh Fruhlinger's As It Happens blog and follow the latest IT news at ITworld. Follow Josh on Twitter at @jfruh_itworld.