rcartier If you look at the picture of the product, you will see a black jumper in the SW socket... It should have been installed already. it serves as a permanently ON setting. If that jumper is missing from your device, then you either have to install a switch connected to those pins, or you can use a jumper from an old computer hard drive. (Jumpers like that one were used to identify which was Master and which was Slave when 2 hard drives were used in older Windows systems. if you don't have an old drive, ask anyone you know who has an old computer in the closet.) If you use an external switch, you can either remove the socket or solder your wires from the back of the PCB. Hope this helps!

rcartier How to play MP3 files on this device from a USB flash drive: 1) USB flash drive must be formatted with fat32 file system (default) 2) Load all MP3 files directly in the root directory, no subfolders. (Files will play in alphabetical order) 3) Insert USB stick into player, and use Mode button to choose USB.

rcartier Yes, but be sure to use a phone charger with it, otherwise your phone's battery will be drained very quickly. If the drive is the big 3.5 inch type, it will need it's own power supply as well as you phone charger. A slim drive, 2.5 inch disc, will get its power from the phone, which is why you need the phone charger.

rcartier No. This item cannot do what you asked. Although it is both a transmitter or a receiver, it can only be one of them at a time. It was not made for two-way communication.

rcartier No. This is a combination charger and protection board only. It does NOT boost the output at all. The maximum output, when the battery is full, will never be above 4.2 volts. If you need a 5 volt output, you will need to add an appropriate boost converter. (Careful, if you buy another board, some will charge and boost, but will not protect the battery.)

rcartier yes.

rcartier Your question doesn't make sense. There is no such thing as a "full-range subwoofer"! Full-range means that it's range of frequencies is close to that of the human ear, 20 Hz - 20KHz. A Subwoofer is a driver that is designed for very low bass frequencies, ~150 Hz and below. I can only assume that you used the word subwoofer to mean driver (or speaker)... In that case, yes, you can use your 10W full-range speaker with a 12V power supply, if the impedence of the speaker is 8 ohms. If the impedence is 4 ohms, you should try it with 12V, and lower the voltage to 9V if you were getting distortion at high volume.