Telephone services known as VoIP are usually not reliable for faxing. VoIP companies use the Internet to route your phone calls. The "I" in VoIP stands for Internet. Because of this, they are able to offer lower costs or a flat rate for unlimited phone calls for their services. The end result is that for faxing, the line quality required is not sufficient to maintain a fax connection. Some well known VoIP companies are: Vonage, Magicjack, Skype, Lingo, Packet8, Teleblend, and others.

Your local telephone and/or long distance company may also offer unlimited long distance calls in a package deal. This type of package usually route your calls over the internet as well. This type of setup is a hybrid VoIP where your local calls are routed through traditional phone systems but your long distance calls are routed through the Internet. You should be able to send faxes to local telephone numbers and receive faxes without any problems. But you may have trouble sending faxes to long distance numbers. Some of these package services are from: AT&T CallVantage, Verizon Voicewing, Sprint Complete Sense, Embarq Unlimited, etc.

There are also digital telephone services from your cable company which may not be suitable for faxing. There are two potential pitfalls with cable digital telephone service. 1) The telephone line is digital. Fax signals operate on analog. Digital and analog do not mix well. 2) Most cable companies route phone calls over the internet.

Using a "cheap" calling card is almost a guarantee that your call will be routed through the Internet.

Technical Description:

Signals from a fax is transmitted as analog sounds through a telephone line. When using a telephone service that route calls through the Internet or a digital telephone line, the sound signals must be converted to digital. The blue line in Figure 1 represents a true analog sound wave. When converted to digital, only an approximation of the sound wave can be reproduced. The green bars in Figure 1 shows the digital approximation. The difference between the analog and digital sound wave is shown in red. Because a true reproduction cannot be attained from analog to digital and then back from digital to analog, that is why faxing is unreliable through VoIP or digital telephone lines.


Figure 1