Originally Posted by MLA
I prefer option #3 and use an illuminated rocker/toggle. Light on = radio = dead battery next trip out.
But, option #3 has the yellow MEM wired to B+ and the rocker/toggle switches the red turn-on wire. this insures that the head-unit sees the same battery reference as the rest of the audio system.
Yes, that is how I pictured #3 option. The rocker has an illuminated indicator light. The yellow would be hot all the time for memory.