The 5500-200 RS-232 I/O Module Plug-In performs the electrical and mechanical interface between EIA RS-232 standard signals and the 5500A Telecommunications Analyzer. The module has two 25-pin subminiature 'D' type connectors; normally made for DCE and female for DTE. DCE/DTE emulation is electronically switchable from the 5500A front panel or via command from a remote terminal over either remote control port