87USB location is belowUSB memory rootModel Name Model Area Product IDAVR4520North America (E3) 000100620100Europe (E2) 000100620200China (E1C) 000100620500+ firmwares+ 000100620100+ APLD.bin+ DSP1.bin+ DSP2.bin+ DSP3.bin+ enc_update.xml+ GUI.bin+ IMG.bcd+ MAIN.bin+ SBL.bcd+ SUB.bin3.4. Insert the USB memory into a USB portNOTE: Please UNPLUG LAN cable from the unit during update.AVR4520 E3DSP1.binDSP2.binDSP3.bin► USB_AVR-4520E3_000100620100-0001 ► firmwares ► 000100620100Download firmwarein USB flash drive.