Metra LC-GMRC-01 GM Class 2 Data Bus Interface Provides accessory (12 volt 3 amp) Retains R.A.P. if equipped Used in non amplified systems or when removing amplified systems Retains warning chimes Uses Micro B USB Provides 12 volt DC 3A accessory output Built in speaker retains warning chimes Designed to be used in non-amplified GM vehicles Retains all the factory warning chimes that would be lost when the OEM radio is removed