The IR senor's on the Slingbox 500 are located on the sides of the unit that communicates to the circuit board inside the unit. The Slingbox 500 does have an External IR port on the back side of the unit that you can plug the External IR Blaster cable in that was supplied with the unit.
If you are looking to use a third party IR Emitter cable, this is not recommended because Sling Media can not guarantee that the cable will work.
Please let me know if you need more information!
Sling Media Moderation Team