Wednesday, 25 August 2010

Fax communications - the poor relation to voice and video

My previous posts in this Aculab technology blog have been mainly on the subjects of voice or video communications, which correlates well with Aculab's main customer activities where our products support services such as voice conferencing, call centre media processing, and interfacing TDM and IP communications.

An oft forgotten technology, still utilised throughout businesses, though perhaps now less prevalent, is fax. We have all been moving our business communications along with the times - investing in mobile solutions, using voice and video conferencing, getting involved in the VoIP communications space, and finding out how Unified Communications and IM might help with business communication efficiencies. Whilst many have been distracted, chasing the latest and greatest way to communicate with colleagues and customers, the humble fax machine has been there in the corner of the office, performing a key function when the newer approaches of document transfer, such as email, did not work or were not suitable.

However, as more and more businesses move to IP-based communications, there comes a time when keeping a single analogue phone line just for the fax machine is no longer economic. To some, it may not matter that a fax is no longer an option for communications. But fax, a 40 year old technology, still plays a key role for many others. There are, luckily, several ways to overcome this dilemma:

Move the fax function to the PC 
Hosted fax services are one approach - pay for a service from providers such as OpenText, Venali, Ring Central and many others, and you get fax capability from your desk. Either a T.37 fax via email approach or a fax server approach using T.38 technology (fax over IP) to enable end users to send a fax from their desks to other similarly equipped recipients or to a standalone fax machine.

Use a T.38 gateway to connect the existing TDM-based phones and fax machines to the IP network
For larger offices, where the uplink is E1/T1 or 'n' x E1/T1, then a gateway is required to provide an IP interface to the core network. A device such as Aculab's ApplianX gateway is perfect for this interface role between TDM and IP networks. A similar T.38 gateway is required at the other end if the fax is targeted at a standalone fax machine.

Integrate the fax machine into an IP-PBX using a simple analogue terminal adapter (ATA)
Perhaps the simplest route forward when the customer still wishes to keep the fax machine.
T38 Fax connectivity using Prosody based fax server and ApplianX.png

The earliest attempts at faxing over IP networks were problematic as they basically attempted to use modem protocols to push a time sensitive signal over an IP network where there was inadequate control over the timing aspects. However, the T.38 recommendation was created to address these issues and has greatly improved the reliability of faxing over IP networks. The only issue to bear in mind is that currently, not all gateways support T.38, so other approaches such as G.711 pass-through still prevail.
If you are considering the purchase of an IP gateway or building a fax server, then you would be wise to make sure you have support for T.38. Aculab's ApplianX IP Gateway is one such gateway, and Aculab's Prosody X media processing board is also ideal when building a high capacity, resilient T.38 fax server.

Andrew Nicholson


  1. The fax machine was able to provide great utility during its time. To be honest, with the wide variety of far better alternatives, I see less use for it.
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  2. It's very easy to understand that now the main point in the internet is to keep all your files safe.
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