Phone Systems Buyer's Guide

Sizing office phone systems

By Sylvia Rosen

When buying an office phone system, your primary concern must be to find a system that is the right size for your firm. Knowing your requirements in advance and understanding system size constraints will help you negotiate with vendors. There are two main factors that determine the size of the system you need:

• Lines. Also called trunks, lines indicate the total number of outside phone lines used by the company.
• Extensions. Extensions are needed for every device within the company that connects to the phone system. Most of the extensions will be for telephones. However, fax machines, credit card terminals, modems, and any other equipment that requires a phone connection must also be tallied.

In key systems, system size is usually indicated as a combination of lines and extensions. For example, a 12 x 36 system accommodates up to 12 lines and 36 extensions. Most PBX systems define size in terms of "ports," which indicate the maximum number of connections that can be made to the system. This includes outside lines and inside extensions, as well as phone system accessories such as voicemail or automated attendants.

Even if an office phone system can handle your current phone traffic, make sure it can also accommodate future growth. The ideal system will expand in a very cost-effective manner. PBX systems allow you to increase capacity by adding new cards that increase the total number of ports available. Some key systems expand simply by adding another cabinet identical to the first.

For planning purposes ask how much it will cost to add extensions, be sure to specify different numbers e.g. 10 vs. 20 vs. 50 additional extensions. Learning the exact method of expansion is not important - what is important is that expansion is easy and affordable.