What is the third prong on a CB radio power wire plug?

I tried installing an old CB radio with a plug with three prongs; two close and the third one set apart a little further. It said that the one set apart was the positive and the one on the other side was the ground, but when connected it drew a ton of power and made the wire get hot, then the radio burned out. Actually first after I realized it was drawing too much, I connected both wires from the close prongs to the ground and it did not draw so bad and the radio powered on but it burnt something out of it.What is the third prong on a CB radio power wire plug?
It sounds like you are installing a Cobra cable to another type of radio. That's not a good idea. If you are installing wires to a radio of brand X then use wires from brand X so nothing catches fire. If you don't, then use regular wires run to a power source. CBs can really push a lot of power so you have to be careful. You more than likely fried something vital and the best thing to do cost wise is buy another radio and don't play with wires.