Overview for Modems

This section presents the key design issues for modems. The Windows operating systems and Win32-based applications use data, fax, voice, and voice/data integration features in modems.

Basic PC 97 modem. The fundamental design principle for compatibility with Windows is for the device to be supported by the Universal Modem Driver (Unimodem), which uses INF files to characterize the behavior of a device. The detailed definition of Unimodem requirements is contained in the Modem Developers Kit (MDK). Future changes will include migration of functions from the device driver into the Windows operating systems and the Win32 Driver Model (WDM).

Also for PC 97, these are the basic design concerns for modems:

• Better Internet access and communications speed. The requirement is for double the speed over that specified for PC 95 (V.34, 28.8 Kbps).
• Better power management. This is both an OnNow design initiative and "Green PC" issue.
• Better installation for improved user experience. This includes requirements for standard commands to allow adaptive installation.
• Required support for data and fax capabilities.
• Recommended support for adaptive connection and standard voice/data, including PC-based video telephony.
• Recommended support for Text Telephones (V.18) to support deaf users.

Voice and voice/data modems. It is only recommended that a modem include voice or voice/data integration features:

• A voice modem communicates in either voice or data mode but does not carry both voice and data simultaneously. Voice-modem applications include telephone answering machine (TAM), automated attendant or receptionist, and interactive voice response (IVR), in addition to conventional person-to-person voice and machine-to-machine data calls. The SOHO (Small Office/Home Office) PC market is driving interest in voice modems that can converse in these various modes over a single analog (POTS) line.
• A voice/data integration modem has the ability to mix voice, data, and optionally video (H.324) in the same call.

In some countries, these features are not yet legal. For some networks, these features are not yet supported (for example, voice/data integration on GSM digital cellular). For some installations, these features have limited utility (for example, modem pools). However, if voice or voice/data integration capabilities are included, the requirements defined in this chapter must be met.

Wireline modems. These are the design issues and recommendations for PC 97:

• Improvements in basic data modem technology, such as V.34 up to 33.6K, V.25ter, and V.80.
• Adaptive connection features: V.25, V.8, V.8bis, and V.25ter Annex A.
• Support voice features, particularly for SOHO or family home use (TIA-695).
• Voice/data integration. The ITU has recently completed work on recommendations for standard Digital Simultaneous Voice/Data (V.70-series) and Video Telephony (H.324 suite) recommendations, along with V.8bis for making the transition from simple voice to a mixed mode. For more information, see the recommendation for simultaneous voice/data integration capabilities later in this chapter.

  In mid-1996, Windows 95 included support for VoiceView, which is a transitional technology, to be followed by support for some form of Simultaneous Voice/Data technology, particularly H.324 video telephony.

Modems for mobile PC systems. The design issues for PC 97 are implementation of analog or digital cellular with standard command sets, as described later in this chapter under the recommendation for cellular phone support. In the short term, Windows and Windows NT can use mobile data and fax. In the longer term, there should be support for voice and Short Messaging Services (SMS).