IP PBX phone systems explained

The aim of this document is to explain the basics of how PBX phone systems work and the benefits to your business. A private branch exchange (PBX or PABX) is a telephone system that organises and distributes calls within an office. The most common products in NZ are Centrex and Gateway.

VoIP PBXs are now basically computer applications delivering off the shelf functionality far beyond the traditional PBX. In addition to standard functions they include features such as call recording, conferencing and call centre functionality previously only found in high end specialist solutions. In additional new tools such as ‘Presence’ are now commonly available which can add significant value to businesses through enabling users to dynamically manage their calling. Read more about the IP phone systems that we recommend.

In the case of a VoIP or IP PBX, users located elsewhere (on mobile, remote workers or other office locations) can also be connected via the phone system as if they were in the same building. There are two main reasons a business which has more than approximately 4 staff (sometimes less) needs a PBX:

Professional Call handling: PBXs offer services such as menu-routing for inbound calls (press 1 for sales, 2 for accounts, etc), DDI dialing, individual voice mail, after hours messaging, hunt groups, call forwarding, extension dialing, remote divert and many other advanced features. IP PBXs also offer internet based services such as voicemail to email functionality, branch connectivity, remote worker access and call recording.

Cost Savings: Having a phone line per person is very costly, as common sense dictates that with 10 people in a typical office it would be very rare for more than six to be on the phone at once. Obvious exceptions are very phone intensive, for example a Travel Agent where everyone might on the phone at once. However although a software company may require that everyone has a phone on their desk for inbound calls, low usage patterns would mean that three or four lines would be more than satisfactory. 

Common Acronyms and PBX Components:

• Standard POTS lines (plain old telephone lines) - the common line used in small businesses. This is adequate only for smaller systems, and usually also carries the businesses ADSL and fax as illustrated. 
• ISDN - the most common digital standard for fixed telephony devices. This can be supplied in either Basic (2 circuit capacity) or Primary (10 to 30 circuit capacity) versions. Most medium to large companies would use Primary ISDN. These lines allow Caller ID and DDI ranges in NZ. 
• SIP Session Initiation Protocol – a common way for two PBX’s to connect voice traffic over data connections (the internet) 
• UPS - we always specify an Uninterruptable power supply to ensure the phone system will continue to function for approximately 60mins in the event of a power failure. 
• IP-PBX or VoIP phone system - this is a PBX that handles voice signals under Internet protocol, bringing benefits for computer telephony integration (CTI). An IP-PBX can commonly exist as physical hardware, or can carry out its functions virtually, performing the call-routing activities of the traditional PBX or as a software only system residing on a server. The virtual version is also called a "Soft PBX". As a rule of thumb traditional ‘appliance type” PBX’s are best suited to all business, except where a business has enterprise level IT support and networks – this is where software based PBX solutions can offer great benefits to large organisations.