The Cisco FRSM-HS1 frame service module (FRSM) is designed for use with the MGX 8220 edge concentrator. The FRSM-HS1/B and FRSM-HS2 FRSMs are designed for use with the MGX 8230 and MGX 8250 multiservice gateways, and the MGX 8800 wide-area edge switch. The FRSM-HS1 and FRSM-HS2 FRSMs offer high-speed serial frame service interfaces for the new world of data networking. The serial port FRSMs offer connectivity to HSSI and X.21 equipment, with the flexibility to operate as DTE or DCE. The FRSM-HS1 provides four ports of X.21 frame services on a single, seven-inch function module. Likewise, the FRSM-HS1/B provides four ports of V.35 on a single, seven-inch function module, while the FRSM-HS2 provides two ports of HSSI frame services on a single, seven-inch function module.