With most businesses using a private branch exchange for their
telephony traffic, we summarise the state of the market and look
ahead to future technology developments.
A private branch exchange (PBX) is an internal corporate network
system that connects a firm's phones, faxes and other communication
tools to the service provider's external public exchange, where the
voice and data calls are routed to the final destination.
Before PBXs came along, every time a staff member wanted to make a
call, they would have to go through a phone company operator first.
The first PBXs very much relied on proprietary systems, which made
it harder for companies to modify them with additional
features.
While some variations still remain in the way different PBXs work,
it is now much easier to modify them to to deliver additional call
features.
However, the future of the traditional PBX is now under question.
This is primarily because of the growth of the internet, and the
resulting possibility to streamline the way voice and data can be
exported out of the enterprise into the public network for its
final destination using voice over IP technology.
Technology issues
There are two main types of PBX: a hardware-based PBX equipped with
the necessary software or a software PBX which routes calls out of
the organisation over a platform such as Windows 2000.
Hardware-based PBXs make up more than 90% of the existing installed
user base. The main reason for this is that a hardware PBX offers a
more secure continuity of service compared to PBXs built on
software alone.
For instance, when backed up with a decent battery system, a power
outage will not knock out the corporate phone system. However, if a
software PBX running through desktop PCs is faced with a similar
problem, or if the servers go down, your staff could be left
without a phone system, depending on how the solution is
configured.
Business issues
The main aim for anyone choosing a PBX system is to make sure that
it can be configured with all the latest call cost-saving measures,
and be able to work with emerging internet technologies designed to
lower call costs.
Any PBX system has to allow for the ability of the enterprise to
take advantage of carrier pre-selection - a technique that allows
corporates to set up their connections with the public exchange
such that different telecoms suppliers can be used for different
types of calls.
For example, a firm should be able to automatically choose BT for
its local calls and Cable & Wireless for its national calls, or
an additional company for its international calls. This can be
achieved without staff having to dial extra digits in front of the
calls they want to make. And it should be able to do this without
having to make any major hardware and software upgrades.
The PBX should also be able to take advantage of technologies such
as VoIP, with companies being able to make some or even all their
voice calls over the internet. Long-distance calls made this way
are charged at a local rate. Because the internet is seen as less
stable than the traditional telephone system, many firms are
choosing to test VoIP in parallel with their existing reliable, but
more expensive hardware PBX.
Management issues
The PBX market is currently at a crossroads. Among the ongoing
issues is whether it is better to buy dedicated hardware or buy a
product that is closer to software designed to run on commodity
hardware. For the SME, another issue is whether to put in place a
system based on local area network telephony.
When choosing a PBX, businesses need to consider the following
points:
- The number of phones in the organisation and usage
- How many sites need to be connected and the amount of traffic
between them
- The location of the main system and its interconnections to
other systems
- Which dial plans and level of resilience best suit your
requirements
- When the peak periods are for network traffic.
Businesses looking to implementing VoIP for inter-office
communications should also ensure their network technology is up to
the job. This means having:
- At least 10/100 megabit Ethernet Lan switches
- Lan switches that interact with and interpret quality of
service features with routers
- Category 5-compliant cabling infrastructure to support 100
megabit data rates and, where applicable, in-line power supply for
IP phones.
Other networking issues to bear in mind are:
- Since the bandwidth in the Lan is often wider than in the wide
area network, you will need to plan the network accordingly with
correct "headroom"
- Ensure that the router and switch networks have enough IP
addresses available to support IP phones and that the routers
support voice compression
- Put in place adequate resilience measures. Businesses should
use a standby power system to maintain a phone network if there is
a mains failure - traditional phones use a central standby power
source.
Suppliers
BT, as the incumbent UK phone operator, still installs most PBXs,
manufactured by a variety of suppliers. BT also installs VoIP
systems.
In the past couple of years Nortel has had a rethink about the way
it approaches the PBX market, acknowledging that the difference
between carrier-class solutions and those necessary for the
enterprise are increasingly becoming narrower.
Cisco has gained BT's support for its new software PBX range.
3Com is offering products that fit between traditional hardware PBX
and a software PBX. It has launched NBX (Network Branch Exchange),
which is powered by a firm's Lan. This is why this solution for
SMEs is called Lan telephony.
Companies such as Mitel and Ascom are among many suppliers that can
help SMEs to get the most out of technologies and applications such
as VoIP and e-commerce. Although the emphasis of VoIP has generally
been on low call costs, the technology can also be deployed to give
users greater functionality. For example, VoIP users can dial from
a desktop screen using highlighted numbers, instead of using a
phone to individually key in all the digits for the number
wanted.
Summary- When choosing a PBX make sure the system is scalable and can be
modified to adapt to future technology changes, particularly if
VoIP takes off
- While convergence of voice and data networks may be the future,
be aware that there are currently shortcomings such as sound
quality degradation compared to a traditional phone line
- Reliability of the phone network is paramount and businesses
should use a standby power system to maintain a phone network if
there is a mains failure. Traditional phones use a central standby
power source but on VoIP networks, IT managers will need to ensure
the network is resilient.