Overview of Different Types of Phone Systems
A PBX (Private Branch eXchange) is essentially an automatic switchboard for telephone systems. It provides the same basic functions for any business or enterprise that the ranks of telephone operators with handfuls of wiring plugs did that you will remember seeing in old movies. Those essential features are to provide switching and connection between any two (or more) telephone users and make sure the connection remains in place until it is ended, at which point the system properly terminates the connection.
Any system that does this automatically for telephone calls within an organization is a PBX. The reason businesses move to PBXes is to avoid requiring every employee to have a direct line to the public telephone system, each of which incurs a connection and a line charge. Instead, a smaller number of lines get shared by all the users and managed by the PBX. This saves money and is more efficient.
IP PBX systems are basically exchange and extension managers for calls based on Internet protocol – also known as VoIP and Internet telephony. The essential advantage they offer to small and medium-sized businesses is the ability to add features that have only been affordable or available to large businesses up to now. VoIP and Internet telephony are usually also more cost-effective when looking at long-term operating costs, due to lower monthly fees and much lower costs to connect and complete calls.
There are three basic kinds of premise-based phone systems. The first kind is called keyless systems or KSU-less systems. They are very lightweight phone systems designed for organizations with fewer than 10 employees that also have very basic phone requirements. The advantage of these systems is that they are very inexpensive and very easy to set up and run. They are portable and can be moved easily if you relocate. However, in a typical keyless sytem, you get very little support and maintenance from your service provider. Also, additional features – such as those that prevent users from picking up a line in the middle of another call – are often impossible to implement. These systems are so simple that they are not considered PBXes and are in fact being phased out since more full-featured PBX systems are approaching them in cost while delivering far more benefits.
The next largest premise-based system is called a key system. These use a KSU (key system unit) that acts as a central control unit, providing features and functions – such as extension management and locking users off from lines that are in use – that aren't available on ordinary phone systems . Key systems are essentially closed, 'black-box' units that provide 80 percent of a basic PBX system's functions for a lower cost. They are typically used in businesses with anywhere from 5 to 50 employees that have only basic business telephony needs. And nowadays, more often than not, key systems are in fact PBX systems with some of the functionality turned off, which makes for an easy path for growth and upgrading should the business need it.
Finally there are full PBX systems, the most common and flexible kind of business phone system. Even a low-cost premise-based PBX can now offer a small business phone services that are indistinguishable externally from those used by multinational corporations.