Private branch exchange, or PBX; key system unit, or KSU; voice over Internet protocol, or VoIP; and KSU-less systems are some good telephone systems. The systems run on different technological platforms.
A PBX system is suitable for both medium- and large-size companies. The system is flexible and can support the complex implementations that many large businesses require. It may have high upfront costs, but its flexibility and advanced customizable features make it economical in the long run.
The KSUs available today provide advanced features suitable for small businesses. In the past, such features were only available with PBX systems. The systems are multi-line and rely on a central control device for connection.
KSU-less systems are suitable for offices that have less than ten employees. They have most of the basic features associated with large systems. The technology is in the phone itself, and the customer can program it to perform specific features. Since the systems are inexpensive, the vendors do not support them, and the customer has to install, program and maintain them.
VoIP makes it possible for offices to connect seamlessly in different locations, both locally and internationally. Unlike the traditional telephone lines, VoIP sends voice calls over the Internet. However, the technology still requires a telephone service provider to connect voice calls. A user can retain the same phone number even if he moves from one part of the world to another.