This article originally appeared in the August 2010 issue of Unified Communications magazine.

Fax, a technology that many may have assumed would have been usurped by e-mail by now, has not been. In fact, some would say it’s stronger than ever, thanks to the evolution occurring in the IP world.

Fax technology has found its footing as a secure method to transfer sensitive information in the enterprise space, such as within the medical and financial industries, where information security and privacy are critical. And while there are still large information distribution fax networks that send literally thousands of faxes per day over traditional TDM and IP-based networks, the popularity of another piece of office equipment, the all-in-one printer, is leading to renewed interest in fax at the small and medium enterprise level.

Many all-in-one office printers now include scan to fax capabilities in addition to traditional printing, scanning and copying. With this useful capability at their fingertips, business people are returning to the fax machine for certain applications. Contracts, purchase orders, NDAs, and other legal documents that require a real signature are the right fit for next-generation fax. While a business owner is probably no longer likely to purchase a stand-alone fax machine and a phone line to go with it, all-in-one machines offer the full feature set that makes fax technology easy and cost-effective to utilize.

Traditionally, voice calls and fax machines were connected over TDM-based networks, such as the PSTN. When IP communications came along, companies that eagerly switched over to IP found that they could easily switch the voice calls, but had to keep a PSTN line for their fax machine due to its intolerance of jitter and delay – common traits of an IP network.

However, the telecom industry has spent a good deal of time and effort developing fax over IP standards and protocols – such as T.38 fax relay – to facilitate large fax distribution efforts. Fax servers connect standard T.30 (PSTN fax) to the IP network for transport and distribution to one or many endpoints using the T.38 protocol. The usage model for fax in recent years has leaned toward the industrial distribution approach rather than direct endpoint-to-endpoint fax transmission. The wider adoption of SIP trunking to provide all connectivity from a business site also will limit the fax options for an enterprise.

T.38 was designed to cope with all the foibles of fax transmissions and provides reliable fax transmission over IP networks, even at the highest (V.34) speeds. However, you cannot currently guarantee that all devices between your sending fax and the receiving end support the T.38 protocol, so there is a need for an alternative solution.

Fax, like a data modem, converts the scanned image into audible tones for transmission. As these tones are typically within the bandwidth range of a standard telephone channel (less than 3400Hz), it is possible to make use of some of the VoIP codec technology developed for voice transmission to enable fax in this relatively new model. T.30 fax can be encoded for IP using the G.711 voice codec with relative ease – a technique known as G.711 fax pass-through. G.711 is an uncompressed codec, so the bandwidth usage is relatively high compared to other codecs used for voice, but the resulting fax transmission can be highly reliable in a well-managed network.

In the typical office use of fax, the momentarily high bandwidth usage for the occasional fax will not materially impact other voice or data services, so this simpler method makes sense. This is an easy trade-off of a less efficient transmission method for a more convenient and cost-effective solution – no fax server hardware, no extra telephone line. However, for the office with significant and regular fax traffic, the T.38 fax relay and fax server use model is the correct choice.

We have heard about the demise of fax for years now, but the usage remains steady, and in some new segments is even growing. It may not be the new kid on the block, but thanks to recent advances in IP-based fax technology, fax continues to march forward as a key component in business communications for many companies.

Andrew Nicholson is a product manager for Aculab (News - Alert) (www.aculab.com).