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Question: Can I fax over an ISDN "modem"?

Question: Can I fax over an ISDN "modem"? Patrick Beart <[email protected]> wonders if software exists that would let him send faxes using his ISDN device: "I use the Farallon Netopia for Mac, and love it. I have been keeping my old Global Village TelePort Gold modem around just for sending and receiving faxes. Seems silly to use a valuable serial port just for this – can I use my ISDN connection instead?"

Answer: Unfortunately, the answer is no. ISDN uses a special kind of phone line which is set up to handle purely digital signals from your ISDN device; fax signals, on the other hand, are entirely analog.

At the central office (or CO) where your phone line enters the phone company’s switching system, your phone line is plugged into one of several kinds of network cards, just like an office network. One kind, the most popular, is for regular analog phone service, called POTS (Plain Old Telephone Service). Others are used for ISDN, and still others for ADSL. So you don’t really have a dial tone as such on an ISDN line, and you can’t place analog calls using an ISDN device.

Most ISDN devices, however, have analog ports in them. These analog ports are created by the equivalent of the network card that the phone company normally would have at its switch. So you can plug a phone line, normal modem, or fax machine into one of these analog ports and treat it just like POTS.

There’s no obstacle we can see to an ISDN device having a cheap, fax-only chipset that would let you fax over one of these analog ports, but we haven’t seen this feature in the $200 to $700 range of devices.

Another option could be to try out one of the Internet faxing services that have sprung up. Many of them are cheaper than the long-distance charges it would cost to send it yourself. Most require special software to be installed, typically Windows-based, to create and send the fax over the Internet to the service. Others enable you to receive faxes over the Internet, using either proprietary software or sending them as file attachments via email.



One of the services that’s received a lot of good press and attention is JFax; they also partner with a number of companies, including Qualcomm for Eudora. JFax provides facilities for sending and receiving faxes using the Internet and software they’ve written for the Mac OS, Windows (3.1, 95, and NT), and Unix. In the U.S., you pay $15 setup and $12.50 a month for a local phone number in one of a few dozen major cities for receiving faxes and voice mail messages. For that fee, you can receive up to 200 "units" comprising any combination of minutes of voice mail and fax pages; additional units are 20 cents each. Incoming messages are sent to you via email, and you use their software to view the fax or listen to the messages. (Contrast this with $30 to $50 per month for a second phone line plus the cost of a decent plain paper fax machine.)


JFax also has a software package for creating outgoing faxes very much like any of the software you would use for directly sending faxes through your modem. Instead, it transmits it over the Internet and sends the fax from their equipment. They charge 10 cents a minute for continental U.S. faxing, payable in advance; that’s cheaper than almost all standard calling plans for home and business. They’ll email you a delivery message so you know the fax was sent. And you don’t need yet another line for faxing or to tie your system up for 20 minutes while it redials again and again.

Given the ADSL options we discuss elsewhere in this issue, it might get to the point where as a home office user, you could have a single ADSL phone line, and do your faxing over the Internet at high speeds. [GF]

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