The 485SD9TB is a port-powered two-channel RS-232 to RS-485 converter. It converts the TD and RD RS-232 lines to balanced half-duplex RS-485 signals. The unit is powered from the RS-232 data and handshake lines whether the lines are high or low. An external power supply can be connected to two terminals on the RS-485 connector if no handshake lines are available. The 485SD9TB has a DB-9 female connector on the RS-232 side and a terminal block connector on the RS-485 side.