There is a power extension wiring harness that provides power to the 8 track. The 8 track then feeds the power back to the am or am/fm radio. There is a switch inside the 8 track player that turns it on when you insert an 8 track and that turns the radio off. Radio comes back and the 8track shuts off on when the 8 track is pulled out. M&H Wiring has the harness, along with the extension harness for the heat sink, and the connections to the speakers. The 8 track uses the 4 stereo speakers that were part of the 8 track option, the radio only feeds the dash speaker, and one of the rear speakers with a balancer knob that came with the U80 option, and also came with the 8 track option.