An in-depth, qualitative analysis and comparison of five telephony systems models.

After exhaustive research on the five main telephony systems models, the following illustrates main points of each model and delves deep into each model's positive and negative attributes.

The five telephony systems are explored in order of least advanced to most.

Plain Old Telephone System: POTS is the original telephony system, a throwback to days when you would share a malt with your best gal and dance to Sinatra on your victrola.

POTS work thusly: telephone wires link a carrier to a business, allowing telephony services to take place. All phones inside the building are connected to this central wire.

Positive attributes:
- Little about POTS has changed since its first incarnation as two tin cans connected by string, but if it ain't broke, why fix it? All non- VoIP telephony systems are based on POTS.

Negative attributes:
-Features are limited by telephone wires; POTS cannot offer the advanced features found in VoIP telephony systems.
-Offers little flexibility, something dynamic businesses need from a telephony system: POTS is entirely dependent on the carrier.
-More expensive than other models, as businesses are charged monthly for each call feature they use.

Key Telephone System: KTS is an updated version of POTS; telephone wires stop at a business's KTS switch instead of going directly to a phone, as is the custom with POTS.

Positive attributes:
-Less expensive than POTS, including more features for less money.
-Expandable, a definite plus in today's fast- passed world.

Negative attributes:
-Akin to POTS, features are limited by transmission over telephone wires.

Central Exchange: CENTREX is similar to PBX, but CENTREX is not privately owned. Instead, CENTREX is owned by a telephone company, who then sells lines and features to a business.

CENTREX is often used by business or companies looking for a temporary solution who plan on later switching to PBX or VoIP.

Positive attributes:
-Carrier is responsible for line maintained, making CENTREX less expensive than other models.
-Provides drastically more features than POTS.
-Good solution for companies that need several extentions with many features, but a PBX is too expensive.

Negative attributes:
-Each line is more expensive than using POTS.

Private Branch Exchange: PBX does away with telephone carriers; a PBX is owned by an individual business, providing telephony service to that business exclusively.

Positive attributes:
-Provides dedicated service unencumbered by telephone carriers.
-Offers many more features than POTS.
-Businesses can easily make the transition to VoIP.

Negative attributes:
-High maintenance cost.

Voice Over Internet Protocol: VoIP is the most advanced telephony systems available, offering advanced features and powerful applications not found in other systems. This is possible because data and voice are transmitted on the same cable.

Positive attributes:
-Eliminates the toll and monthly fees found in other systems.
-Offers advanced features than can help improve efficiency and productivity.
-Increased reliability of the network.
-One line for both data and voice greatly reduces maintenance.

Negative attributes:
-Equipment costs are higher than other models