Clear-Com EF701M

 The EF-701M interface connects one channel of standard or TW party-line intercom to four-wire audio, and simultaneously converts either the DC-voltage call signal or 20kHz call signal to RS-422 data (and back). The resulting four-wire audio plus RS-422 data can then be sent to a fiber-optic converter (modem) or transmitted over twisted-pair cable such as CAT-5. Excellent stand-alone two-to-four-wire converter and hybrid null and wide-range level controls. Easily mounted on a utility rack shelf; up to three units will fit across a standard 1-RU rack space. No additional power connection is required, as the EF-701M is powered by the intercom line.