Dear Brad, I remembered my old program ASDAT. What is ASDAT? It is a DOS tool for capturing and examining captures for capturing and examining data communication on RS232 line. It works on any DOS computer which has 2 serial ports. Using special probe (two 25-pin CANON male/female connectors + two cables connecting probe to serial ports) it captures data + modem signals including exact time information (resolution is 0.05ms). The speed of communication can be up to 19200Bd. Data are stored in the buffer (size is 8kB characters). Data can be saved to disk file after capturing. Data are showed during capture and can be examined after capture ends. There is also possibility of triggering - if you are looking for some special sequence of data on communication line. There is also way to export data from captured file (both directions together or separately). If you are interested in ASDAT I can send you a demo (i.e. ASDAT without ability to capture + some captured files) to try the user interface. I can send you also full version free of charge if you are able to make the probe yourself (BTW 15 years ago ASDAT was being sold for about 5000 CZK - about 250 USD). There was also some other development in ASDAT (new version was written for 32-bit DOS environment): - bigger (nearly unlimited) data buffer - baud rate up to 115200Bd - continuous data capturing to file etc. As far as I can remember the new version was finished but never distributed. ASDAT was never moved to Windows. Regards Cestmir Lengal ClassiCAD, Zlin Czech Republic cleng at classicad.cz