Cisco 4-port Voice/Fax Expansion ModuleCisco 4 port Voice Fax Expansion Module The Cisco 4 port Voice Fax Expansion Module is a compact, enterprise grade solution that extends your Cisco Integrated Services Routers (ISR) with four robust analog voice and fax ports. Built to connect directly to public switched telephone networks (PSTNs) and existing telephony equipment, this module enables seamless integration with Cisco 2821, Cisco 2851, Cisco 3825, and Cisco 3845 platforms. Its designed