LED indicator light?

[Winterz117]

id like to set up my controllers with indicator lights so i know when rapid fire is on without firing 
but i dont know where to wire it in. could someone tell me where in the circuit an LED would go, and what the approx. voltage would be at that point in the circuit?

[gameroms]

what chip you have, what controller you have?

[Winterz117]

i just bought the stuff for the 555 timer method, and i am going to be ordering one of mikes chips for another controller. ones a cheepy controller and ones a matrix board