Does anyone know what CSDB is and where I can get some information on it. Max Technologies has a card out but I can't find anything more along the lines of the parameters with which it operates. I have found things like... COMMON SOURCE DATA BUS.... COMPUTER STANDARD DATA BUS.... COMPUTER SOURCE DATA BUS... and some others that I forgot at this point. It works with serial data transfer between the aircraft and some instruments and other avionic devices. Looking at the connector on the card, it resembles RS422, pin 1 = ground, pin 4 = RX Hi, pin 5 = RX Low, Pin 8 = TX High and Pin 9 = TX Low. I might have the RX and TX groupings flip-floped but thats as much as I can find out. I believe its RS 422 and am going to work accordingly but if anyone knows anything about it, I would really appreciate it if they would tell me what, exactly it is.