Clear-Com EF-701M Encore Audio Conversion 4-Wire InterfaceThe EF 701M interface converts a single channel of standard or TW party line intercom to four wire audio, while also converting call signals to RS 422 data (and back). The EF 701M interface converts a single channel of standard or TW party line intercom to four wire audio, while also converting call signals to RS 422 data (and back). The resulting four wire audio plus RS 422 data can then be sent to a Clear Com Matrix port, ber optic converter (modem)