Centrex (also called Plexar, CentraNet, Centron, Cenpac, Intellipath or Presstige) is a business telephone service offered by your local telephone company from the local central office. Most medium-sized and larger companies use a PBX because it’s much less expensive than connecting an external telephone line to every telephone in the organization. In addition, it’s easier to call someone within a PBX because the number you need to dial is typically just 3 or 4 digits.
But many companies, particularly smaller businesses, may not want to purchase and manage their own telephone system because of the capital investment, technical requirements, or time limitations. Most local telephone companies sell Centrex and lease it to businesses as a substitute for an on-the-business-premisess telephone system that must be bought or leased. Centrex lines usually cost about 20% to 50% more per month than plain analog phone lines. Since local dial tone in the US and Canada is inexpensive, Centrex can be a cost effective way to get the features of a PBX without having to buy a PBX. Centrex may not be for you. You need to compare the rates and features of Centrex to what PBX and key systems have to offer. You need to decide what makes better business sense: leasing Centrex or buying your own switching system. The principal advantages Centrex to small and home-based businesses (called SOHO or Small Office, Home Office) are a low cost of entry, centralized maintenance, and scalability. You get “business phone service” without having to buy equipment (though there are contracts and recurring charges). You can tie together multiple locations under the same four-digit dialing scheme (though many PBXs can also be configured to do this). You don’t need to hire somebody to babysit your phone system. And you can (if your CO has the capacity) expand from five lines to five thousand, without running through several generations of CPE (Customer Premisess Equipment) in the process.