Editing Glossary

; Class 1 : Class 1 fax modems are modems with extensions to their command sets that allow them to act as Group 3 fax machines. Class 1 fax modems leave almost all of the processing to the software. The official standard for Class 1 fax modems is EIA/TIA-578. 

; Class 1.0 : Extension of Class 1 that adds V.34 (SuperG3) high-speed fax capability.

; Class 2 : Class 2 fax modems handle much of the processing previously done by the CPU. It took a very long time for Class 2 to be approved, however, so many fax modems were produced before the standard was official. Thus, Class 2.0 is used for fax modems which apply strictly to the standards, while Class 2 applies to those fax modems that were produced before the standard was official.

; Class 2.1 : Extension of Class 2.0 that adds V.34 (SuperG3) high-speed fax capability.

; DCE : This is Data Circuit-terminating Equipment, which is any device which connects a computer or terminal (DTE) to a data communications network. In the case of fax, this could be a fax modem or other fax device.

; Group 3 : This is a standard for facsimile communications over analog telephone lines originally approved by the CCITT in its T.4 and T.30 recommendations in 1980. This standard is supported by almost all of the current install base of fax machines and fax devices and is continuing to be updated.

; Handshake : An exchange of electronic signals preceding a communication between two facsimile machines to determine the proper connection for transmission.

; PSTN : This is the Public Switched Telephone Network (PSTN) which supports analog voice and fax calls. 

; T.30 : This is the portion of the ITU-T Group 3 facsimile standard which specifies the protocol through which fax devices can exchange information about their supported characteristics and manage the fax session.

; T.38 : This is the ITU-T recommendation which defines a real time method for fax over IP networks.

; V.34 : This is the ITU-T recommendation describing an advanced modulation method which can be used to transmit data at rates of up to 33.6 kilobits per seconds over analog telephone lines (the PSTN).
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 ; Handshake : An exchange of electronic signals preceding a communication between two facsimile machines to determine the proper connection for transmission.
-; ISDN : This is the Integrated Services Digital Network which is an industry standard public digital telephone network. This network is being implemented in the United States and in other countries worldwide as an advanced alternative to the analog telephone network or PSTN (see PSTN).
-; ITU : This is the International Telecommunications Union, which has been the parent body of the CCITT. As of 1993, all the former CCITT telecommunications standards activities will be handled by the ITU Telecommunications Standardization Sector (ITU-T).
 ; PSTN : This is the Public Switched Telephone Network (PSTN) which supports analog voice and fax calls.