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small business pbx planning

October 20th, 2014 by The Modulis Team

Planning a PBX Installation for a Small Business

Smart planning is always at the core of great projects. If you are going to deploy a PBX system within your organization, it is usually a good practice to draw a rough sketch on a whiteboard or a piece of paper. During this planning process, you come to understand the importance of some steps you might have skipped had you moved directly into the execution phase. It is good practice to define the challenges and goals for your business. Once you establish an execution plan, it is easy to design a roadmap to reach your goals. As a basic principle of project management, you should define different stages of your project to include options for future growth and scalability.

For a small business with less than 20 employees

If you have a task to design and deploy a PBX system for a small business consisting of 20 employees, these are the points to be clarified at the beginning of the project:

  • Purpose of the PBX deployment
  • System load and concurrent call load
  • PBX platform
  • Company network
  • Security

Through this process, you develop a clear understanding of why your company needs to deploy a PBX system, what functionalities are needed, the concurrent call loads/capacity, what type of network the company is using, and the security policies in place. By understanding the company network, potential issues of Network Address Translation (NAT), latency or jitter can be addressed. By learning about the security policy, it can be implemented into a PBX design that will protect the company from potential threats to its reputation or products.

To draw a rough sketch of your PBX system needs, use either Word or Excel to create a spreadsheet in the following format to map your extensions:

Once you map the extensions, create a call flow as shown below:

Plan the DID numbers:

Plan time conditions (during what times the extensions should ring–usually during office hours, forward calls to voicemail–usually after office hours, and drop calls–in some special cases, etc.)

An attractive feature in your PBX design is an IVR system as shown below, in which you can design your IVR:

More helpful templates:

Telephone Shortcut Keys:

These templates are essential in helping you sketch a clear picture of a PBX system for your organization.

Once you have completed the first stage of the design, continue with the second stage, which is planning bandwidth requirements according to call loads and capacity. There are many online resources available, but one of the best documents for all hard core VoIP professionals to read regarding VoIP bandwidth planning is:


Once you have gathered enough information, you need to check your PBX solution for the functionalities you require. When you have identified the right solution, you are ready to execute and test your system. Look to Modulis, a leading PBX solutions provider that offers full-scale PBX functionality in addition to various add-on services. Having already calculated your bandwidth requirements, check your company network to ensure it supports that bandwidth or if you need to upgrade. Also check with the service provider to see if they offer enough bandwidth for your traffic load, or if you need to ask for improvements!


For softphones, it is recommend using Xlite, Eyebeam and Jitsi. These softphones are freely available, and you can download the software and have them running in minutes. Eyebeam comes with G.729 support, but in some cases you may have to purchase a license for it. Zoiper and 3CX are good softphones. Zoiper and 3CX have softphone clients available for smartphones.

The choice of softphones depends on the nature of your business. If there is a lot of mobile activity taking place, you may want to select 3CX or Zoiper on smartphones. For desktop systems, Xlite and Eyebeam are the best choices.

What to look for in a PBX system

Some of the most common features you should look for in a PBX system are:

  •  Supported voice codecs (most commonly G711, G729, G723.1)
  • SIP trunking, IAX trunking, DHADI trunking, custom trunking
  • Call waiting, forwarding, conferencing, blocking, recording
  • Voicemail, voicemail to email
  • FAX support, T.38 protocol supported, legacy FAX support, FAX to email
  • A comprehensive management web portal
  • Call logs and system logs in order to check potential issues on calls and systems
  • CRM features if needed
  • Call queuing, ring groups, ACD features (for a call center solution)
  • Support for external databases


There is no specific rule for hardware selection in order to deploy a PBX system. With proper research and some calculations, you can get an estimate of the hardware required to run your PBX system for optimum quality and performance. Some of the parameters to keep in mind while selecting hardware are:

  •  Processing power–good processing power required for high load systems
  • Storage capacity–good storage required for PBXs with many data storage applications
  • Random access memory (RAM)–usually not a big concern with Asterisk based PBXs
  • Network interface cards
  • IP Phones, Analogue Telephony Adapters (ATA)
  • Routers–SIP-friendly routers are recommended for deployment with the PBX

It is best to deploy the PBX system on servers with proper hardware redundancy. This redundancy should be enabled for storage devices (in the form of RAID) as well as for network connectivity elements (redundancy protocols on the switches and servers, like VRRP, HSRP, etc.), so the risk of system failure can be minimized.

Rely on Modulis for a seamless transition, and get your small business on board with a stable PBX phone system.