[an error occurred while processing this directive]


jargon busters mainJargon Busters -
Digital or analogue? - (Dec 1999)
Omtool’s Ken Clark looks for he best way to go in faxing.

[an error occurred while processing this directive]

Fax has come a long way. It’s hard to believe that as recently as 1966 the average transmission time for a page of simple text was six minutes. Then came the Group 3 fax standard, and next up will be Group 4, a fully digital standard which will introduce higher resolutions and colour faxing. Clearly the fax machine of tomorrow will require an ISDN or leased line connection, but what about the fax devices of today? Is there any benefit to be gained from installing digital fax hardware right now?

ISDN and fax

The first thought is that as ISDN offers significantly quicker data transmission speeds than analogue, then fax would be the first to benefit. But, the Group 3 fax standard allows a maximum transmission speed of 14.4kbps on a clear day with a following wind, so whether your fax device is plugged into a humble analogue telephone line or ISDN, you’re still only sending 2 pages per minute.  However, all is not bleak. ISDN uses what is known as out-of-band signaling, and this can reduce connection time significantly. In fact, one ISDN fax device talking to another will connect in less than a second. Once ISDN faxing spreads, those call costs will begin to tumble and that’s not the only advantage ISDN offers.

Firstly, an ISDN connection is infinitely more reliable than any analogue line. Lower line noise and reduced interference means that your faxes will be less likely to fail in mid flow.

Secondly, ISDN fax hardware offers more sophisticated error reporting, so when things do go wrong your fax server can be better informed about its retry strategy. A good fax server product can now tell when it’s dialed a voice telephone line and will not bother trying again.

Direct to your Desktop

Where ISDN really shines is in its ability to bring faxes right to the user’s PC. ISDN allows the assignment of virtual extensions or fax numbers. You could conceivably give a personal fax number to every employee in your company.

DDI (Direct Dial Inward) numbering is nothing new. Chances are you are already using it for your company telephone system to give each user their own phone number. So why not add a personal fax number to your corporate sales executives’ business cards?

Delivery of received faxes is instantaneous to the recipient’s desktop, streamlining your business processes. Fax server technology also makes it possible for road users to dial in and pick up all their fax messages at the same time they get their emails, or voice mail.

The fax server can also make it child’s play to assign DDI numbers to individual users. Add the fax number to your personnel database, or LDAP-compliant email system and have the server look it up on the fly. Ease of administration is key to the success of DDI routing.

At present, DDI routing over ISDN is the only completely reliable medium for automatic routing of faxes to the desktop and although it isn’t cheap, prices are tumbling as a result of tough competition in the market.


Everyone is familiar with Basic Rate ISDN (BRI). Two channels are available for faxing and can be used for receiving faxes by DDI or sending, or both. Digital fax hardware is available now to support one or two BRI lines for two or four lines of faxing, and your telecomms provider will happily assign your DDI numbers across multiple BRI circuits. But for the best bang for your buck, consider PRI. Primary Rate ISDN offers up to 30 fax lines on a single circuit allowing you to scale up your operation at a later date. A six-line PRI solution may look expensive at the outset, but as your fax usage grows you can simply enable additional channels at relatively low cost, completely protecting your initial investment.

For heavy fax users, PRI is the only way to go. With 30 fax lines in a single fax server, well over a million fax pages can be sent or received in a month. The leading financial institutions and law firms sending confirmations of trades, legal documents and so on are already taking advantage of the heavy duty capabilities and reliability that is currently only possible with a PRI-enabled fax server.

As your fax usage grows and your needs change, as new digital faxing standards appear and ISDN becomes more widespread, you can rest assured that your fax server will meet the challenge, delivering leading edge solutions to a technology that seems determined to stand the test of time.

jargon busters main

[an error occurred while processing this directive]