You should be using dual ir emitter cables if possible and the cables should have a 2 pin (mono) plug with a tip and a sleeve. Also, I don't ever use the 'BlinkIR' emitters which have a visible LED inside them such that you can visually see when they are transmitting.
You should also use stick-on emitters and not a direct cabling to IR input jacks on equipment.
Some types of equipment don't tolerate the level if IR that the unit emits. In this case, some have poked a pinhole in black electrical tape and put that on the equipment and then put the emitter on top of the tape.[Link: remotecentral.com]