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+FCLASS=2.0 is the ITU-T-defined value for Service Class 2: a mode in which a computer or other host controls a fax modem through fax-specific commands. It describes the modem’s control interface—not fax image quality or a document format.
What Class 2 fax means
Class 2 is a fax-modem service class. In ITU-T Recommendation T.32, the host system (DTE) communicates with the fax modem (DCE) using a facsimile-specific command interface. The standard identifies Service Class 2 with the setting +FCLASS=2.0.
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In practical terms, the modem handles fax-session control work while the host software issues commands through that interface. The exact commands and options available depend on the modem’s implementation.
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What the +FCLASS values identify
T.32 defines the +FCLASS parameter as a way to report the current service-class setting and the classes the device supports. Its listed values include:
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- DATA/FAX MODE SUPPORT: Data: V.92, V.90, V.34, V.32bis, V.32, V.22bis, V.22, V.23, V.21 Bell 212A & Bell 103; Fax: V.17, V.29, V.27, V.21 Ch 2, EIA/TIA 578 Class 1 and T.31 Fax Class 1.0; DTMF support
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0: data modem1.0: Service Class 1, associated with T.312.0: Service Class 2, associated with T.32
The standards-defined Service Class 2 value is therefore 2.0, even though device descriptions may shorten the name to “Class 2.” A label alone does not establish which commands, options, or extensions a particular modem supports.
How T.32 differs from T.30
The two recommendations address different parts of fax operation:
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- 56K data/fax modem with USB interface, compliant with V.90, and V.42/V.42bis/MNP5 protocols and V.17, V.29, and V.27ter Group 3 fax protocol.
- Support Auto-Dial, Tone and pulse dialing, Auto answer, Auto retrain.
- Support Windows 98SE/2000/ME/XP/Vista/Win 7.
- Support Caller ID and distinctive ring detect, Auto format/speed sensing, Data/Fax/Voice call discrimination, Single configuration profile stored in host, call forward/fallback.
- 2 RJ11 Ports, you can set your telephone, fax system. Up to 56K data download, 48K data upload, and 14.4K fax communication.Provide Quick Connect and Modem-on-Hold features.
| Standard | What it covers |
|---|---|
| ITU-T T.32 | The asynchronous control interface used by a host to control a facsimile modem in Service Class 2. |
| ITU-T T.30 | Group 3 fax document-transmission procedures. |
T.30 describes how Group 3 fax terminals transmit documents over networks such as the general switched telephone network, international leased circuits, and ISDN. T.32 describes how host software controls the modem. They are related, but they are not interchangeable names for the same standard. The ITU-T catalog lists the 2005 T.30 edition and its 2007 V.34-fallback amendment as in force; that status was shown on October 7, 2026.
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- It is not a fax-quality rating. Class 2 does not specify image resolution or indicate that a fax will look better than one sent using another class.
- It is not a page-image format. The term refers to modem control, not how a scanned page is encoded as a file.
- It does not guarantee universal command compatibility. The T.32 label does not prove that two modems or a modem and host program support the same command subset or extensions.
How to verify support on a modem
- Check the modem’s manual or manufacturer documentation for fax service-class support and the commands it implements.
- Look for explicit support for
+FCLASS=2.0or Service Class 2; do not assume compatibility from a generic “Class 2” label alone. - Confirm that your fax software and operating environment support the modem’s documented command set.
ITU-T T.32 (August 1995) defines the standard service-class framework. Manufacturer documentation remains important for understanding a particular device’s supported commands and options.
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- Fax compatibility ITU-T- send & receive rates up to 14.4k BPS, mOh - receive phone call during active internet connection
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- Performance: Support automatic dialing, tone and pulse dialing, automatic answering, automatic fax sending and receiving. Support caller ID, automatic format/speed sensing, data/fax/voice call, single profile stored on the host, call forward/backward.
- Plug and Play: The USB 2.0 fax modem dial-up adapter is suitable for WIN 98 / 2000 / ME / XP / Vista / CE5.0 / 10 / 8.1 / 8 / 7. No need for any external driver.
- Data/Fax Mode: Comply with V.92, V.90 and V.42, V.42bis / MNP5 protocol. Meets V.17, V.29, and V.27ter Group 3 fax protocols. For GRIS fax cats can dial the Internet, send and receive faxes, but do not support voice calls.
- Tech Specs: Up to 56k data download, 48k data upload, and 14.4k fax communication. The 56k data/fax modem uses USB 2.0 Type A with a full speed of 56kb/s.
- Compatibility: Standard and expanded AT command set compatibility. Provides fast connection and maintenance function on the modem.
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