An Introduction to Centrex

by Brian McConnell

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 offer PBX-like services to end users, without requiring customers to buy their own telephone system. This service is generically called Centrex within the industry, although some companies use alternate terms such as Plexar, Comstar, etc.

Centrex telephone lines are really just normal telephone lines which provide extended services, typically including:

  • Three-way calling for conference calls
  • Call transfer (ability to transfer a call to any telephone number)
  • Caller ID
  • Voice mail

Centrex lines usually cost about 20% to 50% more per month than plain analog phone lines (the phone companies tack on a few extra dollars per month for each of these services). Since local dialtone in the U.S. and Canada is already very inexpensive, Centrex is a very cost effective way to get the features of a PBX without having to buy a PBX.

Benefits of Centrex service:

  • It is not necessary to buy your own telephone system
  • Ability to transfer calls to offsite workers (i.e., telecommuters, remote offices, home workers)
  • Ability to grow or shrink your office as needed
  • Service is guaranteed by your local phone company

Current shortcomings of Centrex:

  • No automated attendant; this requires a separate auto-attendant such as Lingo or Sim-phonyNT
  • No ACD (automated call queueing)
  • Move/add/change orders require calling the phone company (this takes time and costs money)
  • Limited call management services (i.e., features like selective call forwarding, do not disturb, follow me roaming, etc., are not available on Centrex)

Products and services used with Centrex

Voice mail and auto-attendant systems
Most phone companies do not offer automated attendant services along with Centrex, or if they do it is very limited in its functionality. The best way to address this is through add-on PC-based voice mail/attendant products such as Active Voice Lingo and Simplified Telephony Sim-phonyNT. These products provide auto-attendant, directory service and voice mail services for your entire office, and can be used to seamlessly route incoming calls inside and outside of your office.

While most telephone companies do offer voice mail for Centrex lines, this voice mail service is somewhat limited in that you cannot redirect your calls to an alternate phone number if you wish to work from another location (i.e., home, cell phone, customer site). So, if you need voice mail and have more than 2 people in your office, you'll probably want to look at these systems fairly closely.

Lingo, from Active Voice, is a low-cost, plug-and-play voice mail/attendant appliance which comes in 2- and 4-line versions. It's inexpensive and designed to work with both Centrex lines, as well as behind popular business intercom systems such as the Panasonic key systems.

The Sim-phony system is a Windows NT-based attendant/voice mail system which is more sophisticated than Lingo as the automated attendant can be custom configured to meet each customer's individual needs. This system starts at around $3,000, and it works as a standalone product, or as a development tool based on Brooktrout's ShowNTel flowcharting application development environment (for creating customized attendant scripts).

TinaTels CTX is a Windows-based system that is designed as a low-cost auto-attendant/CTI solution for Centrex. The price for the software starts at only $199.

Telephones and CTI products
You can benefit from PBX-like feature phones and computer telephony integration (i.e., for screen pops, PC-based dialing, etc.) using smart telephone handsets which are designed to connect to your personal computer. These phones, in addition to being good standalone telephones, when connected to a PC, become a powerful productivity tool.

Virtual PBX service has developed a breakthrough service which provides very sophisticated call management services for companies and workgroups. Their service is an awesome product for companies who work out of several locations, have a lot of mobile workers, or need to deal with telecommuters. Their CrossPoint VirtualPBX service emulates the auto-attendant, voice mail, directory service, and ACD services provided by high-end PBXs without requiring customers to invest in onsite equipment.

Example: a 10-person company with 4 people working from an office, and the other 6 people working from field offices or home offices.

With VirtualPBX service, your company would use a toll-free 888 number to receive incoming calls. These calls would be answered by an auto-attendant which requests an extension number. Each employee has their own extension number (i.e., 101,102,...) which can be dynamically mapped out to one or more telephone numbers. While calls are being routed to individual employees, the caller hears music on hold, and so from an outside caller's perspective, it sounds just like a full-fledged PBX system. The difference is that your employees can be anywhere: at home, in their car, at a customer site, in a hotel, etc., anywhere they can be reached by telephone.

Better still, VirtualPBX offers ACD as part of their service. This means that you can have sales calls distributed evenly to your sales agents, even though they may all be working out of different offices, or on the road. This is a breakthrough capability; you cannot buy a small business telephone system which can distribute ACD calls to offsite users.

ISDN Centrex offers advanced features
If you're looking to go a step beyond the basic call management features offered by regular Centrex lines, you should take a serious look at ISDN Centrex. ISDN (Integrated Services Digital Network) is a next-generation digital telephone service now available throughout most of North America. ISDN lines can be used for both voice and data calls, and offer sophisticated call management capabilities, such as the ability to park multiple calls on hold while conducting a conversation.