the condensor that bolts on to the distributor, what exactly does this do?

i think ive figured out what it is.........a noise filter for the radio?

 

nope, i know what the control module is, but this looks like a cylinder about an inch and a half long and a lil thicker than a pencil. it has one wire grounded to the distributor and it goes to the wiring harness.(thats the way it is on my 83 turbo) it wasnt goin into the wiring harness on my 80 zx i guess the previous owner un hooked it or what ever. the car ran fine with out it, i was just wondering what it is?