SMPVOICE.INF is a sample INF file in the MDK for a voice modem that uses the serial wave driver for playing audio to the handset and line.
In SMPVOICE.INF, the AddReg-type section named [MICROSOFT_VOICE] demonstrates all the registry keys that can be added for voice modem support, along with sample values for each key. See Windows 95 Modem Registry Reference for details about each key. The following paragraphs walk through the items in the [MICROSOFT_VOICE] section to give you an overview of all the keys you can add to the registry for voice modem support.
Note that you must add the name of the new AddReg-type section to the AddReg= item in the Install section for the voice modem. For example, the AddReg= item in SMPVOICE.INF reads
AddReg=All, MfgAddReg, MICROSOFT_VOICE, Modem1.AddReg, PCMCIA