PBX Systems

Overview

A Public Exchange (PBX) is a device that routes phone calls. As it applies to Small Businesses, it is an appliance or server that routes incoming calls to various extensions in the office, and routes outgoing calls from the various extensions to the outside world. As they existed several decades (see picture on the right) a person was required to connect cables between a caller and a callee in order to connect the two. In the days of modern computing, connecting calls can be handled by a computer. And the computer can provide many more functions, such as Voicemail, Time Conditions, and Call Forwarding, and can connect callers and callees to these services.

Choices When Purchasing a new PBX

Analogue or Digital or Hybrid

If reliability is the most important requirement, then you want a PBX that can connect to analogue phones lines.

In the case of those of us living in the Yukon, that means connecting to NWTel phone lines. Special hardware is required to be installed in the PBX computer to connect to NWTel's analogue phone system, making the installation more expensive. Additionally, phone lines are considerably more expensive than the digital options, making the ongoing expense of maintaining your PBX higher. The benefit to having a system that can use analogue lines is that down time of the system is typically going to be less than 8 hours per year, achieving a 99.999% uptime (5 nines).

Digital phone lines, often referred to as VoIP, are considerably less expensive than analogue. Phone lines are still purchased in the same way they are from NWTel, but they come from a VoIP provider, and they work over an existing internet connection instead of a dedicated copper wire. No special equipment is needed for the server, and the lines are far less expensive. Additionally, most VoIP services provide free long distance calling in Canada, and free or pennies per minute calling the US. Additionally, calling to worldwide numbers is generally very inexpensive, though that is not true of every single foreign country. So there is a very strong economical argument to use digital phone lines. The downside to digital lines is that they cannot be any more reliable than the internet, so one can expect to have about 2-4 days of down time across a year. Often that comes in the form of a few hours at a time which accumulates to a few days by the end of the year, but it can potentially include a full day of downtime.

Hybrid systems provide the best of both worlds. It can save a lot of money by allow the inexpensive or free long distance calling, but still requires installing the special hardware in the PBX server and having analogue lines from NWTel. The PBX server is configured to send outgoing calls through the VoIP provider by default and fail over to the analogue lines when all VoIP lines are in use, though any combination of restrictions can be configured. Another limitation to hybrid systems is that they have 2 phone numbers; one from nwtel, and one from the VoIP provider, and when you call a callee, their phone will display a different number depending on which service the call goes out over, and someone calling into the system can use either number.

Once all the lines are in simultaneous use, no additional calls will be possible into or out of the system. When choosing the number of lines you want, you will want to guess how many maximum concurrent calls will be in play at any given time, and add one line just in case someone calls in while all the other lines are busy. If all lines are busy and someone calls into the PBX system, that caller will get a busy signal. One thing to note with hybrid systems is that while outgoing calls can fail over from the VoIP provider to NWTel phone lines, incoming calls cannot. So if all VoIP lines are occupied with outgoing calls while someone calls in to the number provided by the VoIP provider, they will get a busy signal even if none of the NWTel lines are occupied at all.