Manufacturer’s claims aside, you can easily verify that a modem does in fact provide the voice support required. To do so, follow these steps:
1. Open the Windows Control Panel
2. Open Phone and Modem options.
3. Select your modem.
4. Click on Properties
5. Select the Advanced tab
6. Click on Query Modem
The response will include a line that begins with: AT+F class =
If this line includes a ,8 at the end, then you have voice modem support.
(e.g. AT+F class = 01,8)
If not, then your modem does not have the required voice support.