BOSS Audio Systems 637UA Single-DIN CD MP3 Player Receiver, Detachable Front Panel;

Feel the miles zoom by while you listen to music on the BOSS Audio 637UA CD/ MP3 Player. Play your favorite CD, listen to the AM/FM radio or hook up your smartphone or MP3 player through the Auxiliary input. You can also plug into the USB port for your own playlists. Choose your sound style with the Preset Built-in EQ. To prevent theft, detach the front panel when you leave. Take the BOSS Audio 637UA for a spin and enjoy great sound on the road.

There are three main wires that should be connected to the power supply to turn ON the radio.

1. Yellow - Constant Source +12 VDC like the (+) Positive post of the battery
2. Red – Switched Power +12 VDC normally connected to the ACC line of the Ignition key
3. Black - Ground (-) has continuity with chassis ground
4. Both RED and YELLOW wires should have +12VDC on the line and the BLACK wire should be connected to GROUND for the radio to turn ON.
   
5. In instances that the BLACK wire is connected to the GROUND while either one of the YELLOW or RED is connected to the +12VDC, the unit will not turn ON. All three wires should be connected to their respective terminals or connectors.
6. For testing the unit out of the vehicle, the RED and YELLOW should receive +12VDC and the BLACK should be connected to GROUND.