Low-pass filter and level control (sub preamp output). Inputs: front panel auxiliary, SD card slot, and two USB inputs (one 1A USB port is for charging only). Outputs: 5-channel preamp outputs (4-volt front and rear, plus 3-volt mono sub). Also if you are in AK, HI, PR, U. The item "NEW Nakamichi NA788 DOUBLE 2 DIN CD/MP3 Player Bluetooth Front USB AUX SD Slot" is in sale since Monday, June 22, 2020.This item is in the category "Consumer Electronics\Vehicle Electronics & GPS\Car Audio\Car Audio In-Dash Units". The seller is "autosounds_warehouse" and is located in Rosemead, California. This item can be shipped worldwide.