The straight is as it says, the null has two wires crosed, off the top of my head can't remenber which ones 2/3 or4/5 anyway doesn't matter there different because or this.
Want to know what cable you need to flash that shiny,new receiver ? There are two types of cables used, and both look the same on the outside, but are wired differently internally. They are the straight DB9 RS232 female to female cable, and the Null 9 pin RS232 female to female cable. The straight DB9 cable has all pins connected the same at both ends(pin 1-1, 2-2,3-3,etc.). The Null cable(also known as a Null-Modem) has pins 2 and 3 crossed(pin 2-3, 3-2). You can use a straight DB9 cable to program receivers requiring a Null cable, by purchasing an inexpensive Null adapter to attach to one end of the straight DB9 cable. This allows one cable to be used for any receiver.
Here is a list of the most popular receivers on the market and the cable needed to program them.
Ariza Ultra 400/500- Null Astrovox 2600-Straight DB9 Blackbird and all Blackbird clones(BOB, Max 1000, Stealth II, MS1000, ,etc.)-Null Coo*lsat 4000 Plus-Null Coo*lsat 4000 Pro-Straight DB9 Cooltec-Null Coship (All)-Null Digiwave 6800/7000-Null Digiwave Diamond-Straight DB9 Dreambox (All)-Null Fortec lifetime-Straight DB9 Fortec Lifetime Ultra-Straight DB9 Lava 2600-Null Max 2500-Null ****sat (All)-Straight DB9 Microroyal (All)-Null Pansat 2300a/2500a and all clones-Straight DB9 Pansat 2700-Null Pansat 3500-Null Pansat 5000HC-Null(Also can program through USB) Pantec/Multistar Max (All)-Null Pantec/Multistar MS (All except MS1000)-Straight DB9 Pantec MX/Ultra-Straight DB9 Rex1-Null Silver bullet/ST 1000/2000-Null Skyview 500-Straight DB9 Spacestar DVB500-null Stealth 2000a-Null Ultrastar 5000-Null Viewsat VS2000-Null _________________ Current Dishnet and Bev keys, Key Finders, and ECM Info: http://www.dsscommunity.c*om/forums/index.php?c=22