Fax class

 

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The service class of the fax modem describes the specification that a PC uses to communicate with the fax modem. The most common classes of fax modem are Class 1, Class 2 and Class 2.0. These classes are specified as extensions to the Hayes command set.

 

Fax class 1

 

A class 1 fax modem is little more than a data modem with a few extra frequencies that are necessary for group III fax transmission.

 

Fax class 2

 

Class 2 is a higher level specification than class 1. More of the fax protocol work is done within the fax modem firmware. This fax service class specification was never formally approved by the ITU.

 

Fax class 2.0

 

Class 2.0 is similar to the Class 2 specification, but has been formally approved by the ITU.