All rights reserved. When you buy Centrex, you're essentially leasing a piece of an Ameritech central office. So, instead of having to buy costly switching equipment, which you would have to maintain at your office, you're reserving dedicated lines and switches at an Ameritech facility. Purchase of switching equipment is necessary. It's easy to upgrade, without disruption of service.
Upgrades can cause service disruptions.
Services can only be added on a system-wide basis. Redundancy and reliability is built in. Redundancy must be added at substantial cost. Offers high reliability at no added cost. You have automatic battery backup during power failure.