Registered fax the document to be sent and the resulting multipage image is encapsulated in an electronic envelope file format that allows time stamp insertion as meta data or as a specific tag.<br> - This envelope document is digitally signed using non reversible cryptography elements and the signature is then printed on the last page of the document for facsimile transmission.<br> - The receipt of the fax acknowledgment and subsequent transmission report validates that the content has been delivered in full to the receiver, including the page containing the signature and informing the receiver about the certified nature of the facsimile transmission.<br>
Internet fax However after the development of open source IP PBX systems, it become common to set up a fully software-based email to fax or Web to fax gateways. like Asterisk (PBX) and ICTFax. Making phone calls over the Internet (Voice over Internet Protocol, or VoIP) has become increasingly popular. Compressing fax signals is different from compressing voice signals, so a new standard (T.38) has been created for this. Using a (sending) VoIP adapter and (receiving) gateway which are both T.38 compliant, most fax machines can be plugged into the VoIP adapter in the same way as to a regular phone line.