1) It requires the application module DPOXCOMP.  X refers to the different model.  For example, DPO2000 requires the DPO2COMP. 2) It uses the RS232 bus decode, however, the polarity need to be modified to “Inverted” There are two other types of variants on the RS-232 family that are also addressed with the DPOXCOMP. The first is differential signaling, such as with the RS-422 and RS-485 standards. These standards specify transmission of a lower-voltage differential signal which is not inverted. Although one side of these differential signals can be probed with a passive probe, theTDP0500 and TDP1000 differential probes will provide better signal fidelity, especially in noisy environments. The second variant on RS-232 signals is the transmission of these serial signals between components on a single circuit board. This embedded system application, most commonly communication between a microcontroller and a Universal Asynchronous Receiver / Transmitter (UART) or RS-232 driver/receiver IC. These signals are single-ended and non-inverted, with standard logic levels. For both of these non-inverting RS-232 variants, you need to select the Polarity Inverted (High = 1) side bezel button in the Bus Define Inputs Menu. Otherwise, the signals are treated like RS-232 signals. For additional information please see http://www.tek.com/support/faqs/do-you-have-detailed-application-note-how-use-dpo-mso4000-series-oscilloscopes-debuggin.