1. KEY SYSTEM UNITS (KSU)
This is the PBS that is most suitable for small businesses (since a small business has a less complex interconnectivity needs and so less number of phone lines can be conveniently supported) in managing their incoming and outgoing calls because it supports only the basic telephony functions. Thus, it is equipped with buttons or keys that enable the operator to select incoming and outgoing calls; ascertain the status of both lines and extensions; and enhance connections between extensions and other external lines.
2. PRIVATE BRANCH EXCHANGE
As the name suggests, the private branch exchange (PBX) system is a private phone network which is accessible to only the members of the concerned business. For small businesses planning to grow as well as businesses demanding a minimum of forty (40) lines, the private exchange system is definitely the best business phone system to go for; it can handles higher volumes of in-coming calls than the KSU. Thus, the higher the number of the business associates (employer, partners, and employees) in one business branch, the higher the capacity of the private branch exchange needed to be installed in that branch. Therefore, one PBX can support tens and even hundreds of phone calls. Recent advances in technology have made the PBX easier to use as there are now digital PBXs in existence, even as analogue PBXs still exist. The digital PBXs are incorporated into computers which can now manage and even switch the calls.A BRIEF HISTORY OF CLOUD TELEPHONY
Telephone as a concept of its own can be traced back to the era of the string telephone, which was also called the lover's telephone, which existed centuries ago. It comprised of two diaphragms which were connected together by means of a wire or taut string. This was the basis on which the children's toy (called tin can telephone) was made, by connecting two strings to the bottom of two metallic can or paper cups. With time, technological advancement saw the innovation of entirely new models by different individual, the patent credit of which drew a lot of lawsuits.
The additional features of PBX which the KSU does not have include: the ability to support call logging, fax and computer modern integration, individual voicemail, call transfer, as well as automated routing to individual extensions (a feature called direct dial-in or DD). The PBX system adds flexibility to business management because it supports being hosted on-premise and its switchboard system can be managed on-premise as well. To add to its flexibility advantage, the PBX system allows one to choose to either to operate the switchboard virtually in the cloud or a third-party provider can be employed to manage it.3. VIRTUAL PHONE SYSTEM (VPS)
Unlike the PBX which supports only a single branch phone system operation, the virtual phone system delivers all the features of the PBX over the internet. Delivery over the internet enables workers to stay connected despite their location they may be. Therefore, this system can also be called a virtual PBX since it’s still only the workers that can access it and so privacy is still intact. Voice over internet Protocol (VoIP) can be incorporated into Virtual PBX enabling additional features such as document sharing, instant messaging, video calling, and even video conference. VoIP offers a wide range of features ranging from call forwarding, call blocking, caller ID and voicemail, to remote management, automatic call distribution and interactive voice recognition. Also, VoIP saves cost as one just has to pay for only internet connection; internet calls between individuals with VoIP is entirely free!
The flexibility of Virtual phone systems makes them suitable for both on-premise systems as well as small and large businesses, unlike the traditional systems. Since they are delivered over the broadband connection and can as well work with existing phones (all types of phones including landline and mobiles), they do not need extra hardware. Consequently, they usually require lower start-up costs for businesses that need to install them.