[. . . ] 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. [. . . ] Do not allow the wire to directly contact the edge of the iron plate by using Grommets. Connect the ground wire to a metal part of the car chassis that acts as an electrical ground passing electricity to the battery`s negative - terminal. Be sure to install a protective fuse in the power cord near the battery. For the power cord and ground, use a vehicle type (fireproof ) power wring cord with a current capacity greater than the unit's fuse capacity. ) · When more than one power amplifier are going to be used, use a power supply wiring wire and protective fuse of greater current-handling capacity than the total maximum current drawn by each amplifier. 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. The installation to the vehicle should securely fasten the unit to a place in which it will not obstruct driving. If the unit comes off due to a shock and hits a person or safety part, it may cause injury or an accident. After installing the unit, check to make sure that electrical equipment such as the brake lamps, turn signal lamps and windshield wipers operate normally. If sound is not output normally, immediately turn power off and check connections. 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. [. . . ] As this unit accepts speakers with a minimum impedance of 1 ohm, connect speakers with 1-ohm or higher impedance to these terminals. The rated input of the speakers should be no less than the maximum output of the amplifier. 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. The genuine-accessory car stereo shall have a maximum power output of no more than 40 W. [. . . ]