I just got a65 AM radio to replace the Sparkomatic AM/FM radio that was in the car. It has 3 tabs in the back corner of the radio. I can't find anything on the rest of the internet as to what each tab is for and the connector on the car is no longer there. Do any of you know the purpose of each tab? I am assuming one is hot, one is ground, and one is speaker, but then maybe ground is the case and two are speakers? Any help is very much appreciated. Thank you!