Cisco High-Speed - Expansion module - RS-232 x 2 - for Cisco 18XX, 1921 4-pair, 1921 ADSL2+, 1921 T1, 19XX, 28XX, 29XX, 38XX, 39XX, 39XX ES24

Dial access server. Asynchronous HWICs can connect to external dial modems to provide low-density dial access servers. Legacy protocol transport. Serial and synchronous/asynchronous ports are ideally suited to transport legacy traffic across a TCP/IP network, facilitating network convergence and eliminating costly separate leased lines for this traffic.