The VCL E1 (G.703) Fiber Optic Modem provides the user the capability to establish communication between two E1 interfaces or between an E1/FE1 interface and a "n"x64 V.35 interface over an optical fiber link. It establishes a secure, long range data fiber link between routers, multiplexers and other E1 devices. The primary application for the VCL-E1 (G.703) Fiber Optic Modem is to establish point-to-point fiber link at ranges longer than any copper modem can achieve. The clock options are Internal/External/Slave Clock - three clock mode option.