The Cisco IP Communications voice/fax network modules provide enterprises, managed service providers, & service providers the ability to directly connect the public switched telephone network (PSTN) & traditional telephony equipment to existing Cisco 2600XM Series, Cisco 2691, 3640, & 3660, & Cisco 3700 Series voice gateway routers. This set of Cisco IP Communications voice/fax network modules delivers the most versatile combination of analog & digital voice & data capabilities in a single network module. The 4-port FXO voice/fax interface card is a universal card, which can be software configured to work in all countries. FXO port is used to connect to PBX or key system, or to provide off-premises connections to PSTN or PTT. Supports battery reversal detection & caller ID.