What modems are support the AT command of activate voice?

Q2604 supports analog audio but no USB interface.

Design guideline for reference:
http://archive.sierrawireless.com/Download.aspx?File=%5CAirPrime%5CQ240x%5CSierra%20Wireless%20AirPrime%20Q2406_Q2426_Customer_Design_Guidelines_rev007g.pdf