What is the standard protocol that all G3 faxes support?

The standard protocol that all G3 faxes support is T.30. This protocol outlines the procedures for the establishment and control of fax communications, including the transmission of documents over a standard telephone network.

In the context of G3 faxes, T.30 serves as the foundational protocol that ensures interoperability among different fax machines and establishes a reliable method for sending and receiving fax documents. It defines the signaling and data protocols necessary for a successful fax transmission, which includes handshaking procedures, error correction, and transmission speed negotiation.

The other options specifically relate to different functionalities or advancements in fax technology. For instance, T.37 is related to the transmission of faxes over email, while T.38 is designed for fax over IP networks, providing a way to transmit faxes in real time using VoIP. G.711 is an audio codec used for compressing voice data and is not specifically tied to faxing procedures. Thus, T.30 is the correct choice as it is inherently linked to the operation of traditional G3 fax devices.