Go to the guys selling computer parts. Buy an rs 232 cable (as shown in Diagram 1). You can take the picture along with you for them to understand. Both ends of the cable should be female (with holes) See attached diagram. The connections will be
pin 2-----------------------------------pin 3
pin 3-----------------------------------pin 2
pin 5-----------------------------------pin 5
Though it may be difficult for you to physically know what connects to what, i will give you my own style.
Take a cutter (or knife, pliers) and cut your cable into 2 at the midpoint (middle), you will find 9 coloured cables including a Unclad one. You will only need the Green, Orange, Red and the Unclad cable. Connects it like this at both ends.
END 1 END 2
Red ------> connects to <----------- Orange
Orange ------> connects to <----------- Red
Green -----> connects to <----------- Green
Unclad wire ------> connects to <----------- Unclad wire
If you connect it well, then you are good to go. (make sure you cover the connected ends with cello tape before you destroy your decoder oooo)