I am trying to determine if the documents I send from my office fax machine are encrypted/secure or not.
I found this article which kind of explains the current state of fax security:
According to Ontario, Canada based Natural Data, Inc., there are over 100 million fax machines in use worldwide today. Almost all of these fax machines are unable to connect to the Internet and as a result can only send and receive faxes using the unsecured public fax line services.
But that doesn't really help me assess whether my particular fax connection is secured or not. How do I know if my fax machine is networked? Even if it is networked, how do I know if it's secure? How secure is it (AES, PGP, etc.)? Is there an unsecure/secure dichotomy in the fax protocols (T4 & T30) like you have with HTTP/HTTPS and FTP/SFTP?