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Integrating Fax With VoIP info@smart-bridge.net

Traditional fax devices use what is known as a T.30 protocol which specifies the encapsulation of faxed documents over the PSTN network. As you know, from a hardware point of view the fax line is just a regular telephone line which plugs into the PSTN network as usual and has its own telephone number. When we implement a VoIP system, we have to pay special attention to the fax infrastructure because by itself the fax system doesn't play well with VoIP protocols and codecs. The reason is that audio codecs used by VoIP are optimized for voice data. When we utilize the same algorithms on faxed documents the result isn't what we expect. In addition, the T.30 protocol shows no tolerance for the unique features of the Internet such as lost packets, occasional disconnections etc. For this reason, a new protocol had to be developed for fax alone called the T.38 protocol.

If you're using a hosted PBX provider, this special T.38 protocol has to be handled at their end. This is because a typical use case scenario for receiving a fax will be a person on a PSTN network with a traditional fax machine sending you a document. The signal will reach your SIP provider still using the T.30 protocol since the PSTN network is unaware of the fact that the end-user is on a VoIP network. Your SIP provider has to take that signal and transform it into a T.38 one which will then be sent to your business location. If you have a traditional fax device, you know that you need to use it with what we call an "ATA" which converts the digital signal into analog and vice versa. Your fax machine will plug into this ATA and will not realize that the signal it is getting is actually on that is generated by it.

The simple use case scenario can have any variations. You can configure your VoIP network so that you can do away with the fax machine entirely. All incoming faxes can be converted to a PDF and mailed to you depending on the services provided by your SIP provider. Sending a fax might be accomplished by scanning the document and encoding it using the T.38 protocol. This will be handled by the appropriate software of course.

The emergence of VoIP systems creates many ways by which businesses can choose to handle the sending and receiving of faxes. Contact your ITSP to find out what they recommend and how you can customize the solution to work with your organization