IP PBX

IP PBX Hardware

Refer to the diagram to the right.  Click on the diagram for a larger version.  For an explanation of terms, see our page on "What is IP Telephony?"

The IP PBX Itself

The IP PBX is a computer, plain and simple. For most simple PBX's this does not even need to be a particularly powerful computer, as the computing needs are very simple.  The PBX runs software that does all of the telephone "magic."  This includes direct inward dialing, call forwarding, call transfer, call parking, voice mail, and so on.  Some of the software available is proprietary, meaning that you pay (usually a lot) for the software alone.  Other software is what is known as "open-source," in which the software is not developed by one individual or one company, but by volunteers throughout the world making additions and changes.  These usually run on Linux, a well-known, well-thought of open-source operating system.  If you are ambitious, you can take a computer, download the Linux, and the PBX software, and install it all yourself, and have a PBX for free.  The PBX is connected by normal network cabling to the POE Switch.

POE Switch

A switch is a network device that transfers the network packets from the sending computer to the receiving computer.  Almost all networks have a switch at its core.  A POE (Power Over Ethernet) Switch is used with IP PBX's because they can provide power for peripherals over the network cabling.  A POE switch is not absolutely necessary, but without one, you have to have external power supplies for the telephones.  The POE switch does away with the need for these "power bricks," reducing the office clutter, and receptacle usage.

IP Telephones

IP telephones are special telephones that use network cabling.  They are in fact small computers themselves.  They operate just like any other telephone.  Standard analog phones can not be used as IP phones, though they can be attached to the IP PBX by means of an ATA.  Proprietary digital phones from proprietary PBX's can not be used.  Many IP telephones have built-in two-port switches, so that the desktop computer can share a single network connection with the phone, often eliminating the need for additional cabling.  IP phones are available from all of the better telephone manufacturers:  Aastra, Polycom, Cisco, Avaya, 3Com, etc.

There are also softphones available.  A softphone is software that runs on a computer, and provides all of the functionality of an IP phone.  They require either headsets, or computer speakers and microphones attached to the computer.

Analog Telephone Adapter

PSTN lines and telephone devices are not directly compatible with an IP PBX.  The signal is not digital.  The analog signal needs to be converted to the digital signal using the IP protocol.  Analog adapters do this.  They connect to the network, and to the analog device or system.  There are two different types of adapters, in and out (FXO and FXS, for you techies.)  The in adapters connect PSTN phone lines to the PBX.  The out adapters connect telephones, analog PBX's, answering machines, and so on, but answering machines are generally not needed, as most PBX's incorporate voice mail, including sending the voice mail to e-mail.

That's all there is to it!  Everything else is just the standard network.  Be sure to check out our business case for an IP PBX.