Microsoft KB Archive/107393

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Fax Modem Class Required for Binary File Transfers

Article ID: 107393

Article Last Modified on 10/30/1999


  • Microsoft Windows for Workgroups 3.11

This article was previously published under Q107393


With Microsoft At Work PC Fax version 1.0 (supplied with Microsoft Windows for Workgroups 3.11), if you want to perform binary file transfers or use the advanced security features, you must use a Class 1 fax modem at both ends of the communication. This article provides instructions to determine what class of fax modem you have.


Use the following procedure to determine what class of fax modem you are using:

  1. Load the Terminal application provided with Windows for Workgroups and configure it with the correct settings for your modem.
  2. In the Terminal window, type the following:


The modem should respond with one of the following strings of numbers:








These strings can be interpreted as follows:

   0 = Data

   1 = Class 1

   2 = Class 2

Class 1 and Class 2 are standards that define an interface with an asynchronous serial bidirectional data stream between the computer and the fax modem. Fax modems can be members of more than one fax class. For example, if the result of the above procedure was "0,1,2," the fax modem would belong to the Data, Class 1, and Class 2 categories.

Microsoft At Work PC Fax software can send a fax as a graphical image (facsimile format) or as a Microsoft Mail message in binary form (electronic mail format).

The ability to send a fax in binary form allows you to send attachments, such as Word for Windows documents or Microsoft Excel spreadsheets, to remote locations without having to use communications software (such as Terminal). These attachments can also be edited, whereas a fax transmitted in the facsimile format cannot be edited.

Without a Class 1 fax modem on both the sending and receiving ends of a fax transmission made with At Work PC Fax, faxes always transfer as graphical images that can be viewed and printed only.

At Work PC Fax also provides advanced security features to ensure the security of faxes by encrypting them. An encrypted fax cannot be read by anyone except the intended recipient. These security features include password encryption, key encryption, and the ability to apply a digital signature to the fax.

To use the security features provided by At Work PC Fax, both the sender and the recipient of the fax must be using Microsoft At Work PC Fax and Class 1 fax modems so that the fax can be transmitted in the electronic mail binary file format.

Additional query words: 3.11 type E-Mail

Keywords: KB107393