[. . . ] When the unit malfunctions and a DC signal is sent to the speaker output. When a ground wire of the center unit (cassette receiver, CD receiver, etc. ) or this unit is not connected to a metal part serving as an electrical ground passing electricity to the battery's negative - terminal. To prevent damage to the machine, take the following precautions: Be sure the unit is connected to a 12V DC power supply with a negative ground connection. [. . . ] If you experience problems during installation, consult your Kenwood dealer. If the unit does not seem to be working right, consult your Kenwood dealer. Changes or modifications to this equipment may cause harmful interference unless the modifications are expressly approved in the instruction manual. The user could lose the authority to operate this equipment if an unauthorized change or modification is made. This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment may cause harmful interference to radio communications, if it is not installed and used in accordance with the instructions. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one or more of the following measures: · Connect the equipment into an outlet on a circuit different from that to which the receiver is connected. The rated input power of the speakers that are going to be connected should be greater than the maximum output power (in Watts) of the amplifier. Use of speakers having input power ratings that are less than the output power of the amplifier will cause smoke to be emitted as well as damage. Be sure to turn the power off before changing the setting of any switch. If the fuse blows, check wires for shorts, then replace the fuse with one of the same rating. Do not remove caps from unconnected wires or connectors to prevent short circuits. Sharing the negative wire of the speaker or grounding speaker wires to the metal body of the car can cause this unit to fail. After installation, check that the brake lamps, winkers, and wipers work properly. Gray/Black Genuine-accessory car stereo (No line output center unit etc. Do not connect cables and leads to both RCA cable input jacks and the speaker level input terminals simultaneously, for this may cause malfunction or damage. Lead terminal* Terminal cover Battery wire* Protective Fuse* Right speaker Left speaker Remove the cover to access to its controls for adjustment. The genuine-accessory car stereo shall have a maximum power output of no more than 40 W. Do not connect the speaker output leads from a power amplifier (Optional) to the speaker level input terminals of this unit, for this may cause malfunction or damage. Do not connect cables and leads to both RCA cable input jacks and the speaker level input terminals simultaneously, for this may cause malfunction or damage. [. . . ] When multiple speakers are to be connected, ensure that the combined impedance is 4 or greater. Set this control according to the pre-output level of the center unit connected with this unit, or to the maximum power output of the genuineaccessory car stereo. For the pre-output level or the maximum power output, refer to the <Specifications> in the instruction manual of the center unit. The rated input of the speakers should be no less than the maximum output of the amplifier. [. . . ]