The SN75186 is a low-power bipolar device containing four driver/receiver pairs designed to interface data terminal equipment (DTE) with data circuit-terminating equipment (DCE). Additionally, the SN75186 has a loopback mode that can be used by a data communication system to perform a functional self-test on each driver/receiver pair, removing the need to locally disconnect cables and install a loopback connector. Flexibility of control is ensured by each driver/receiver pair having its own loopback control input. The SN75186 is designed to conform to standards ANSI EIA/ TIA-232-E and ITU Recommendation V.28.