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Model 485LP9TB is a port-powered, two-channel converter. It converts TD and RD RS-232 lines to balanced RS-485 signals. The unit can be powered from the RS-232 handshake lines, DTR and RTS. If port-powering the unit, one of these handshake lines must be asserted (high) in order to power the unit (See Table 1). DTR must be asserted to receive data. The RS-485 driver is enabled when RTS is asserted and disabled when RTS is disasserted. The RS-485 receiver is disabled when the driver is enabled and is enabled when the driver is disabled. _x000D_
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To maximize the amount of power available to the RS-485 driver, the RS-232 handshake lines are not looped back (tied together). As a result, the following handshake lines will appear as disasserted (low): CTS, DCD, and DSR. Care should be taken to ensure that any software being used does not require any of these handshake lines be asserted. If existing software requires any of the handshake lines to be asserted, you can loop back the required handshake lines in your cable.