Key operating instructions:
The "Prev/V--" key : " short press "is switching to"the last song ,"long press" is for "volume decreasing"
The "Next++" key : " short press "is switching to"the next song","long press"is for"volume increasing "
The "P/P/Mode" key :"short press"is switching to "play / pause", " long press"is U disk and TF Card mode's selection
The "Repeat" key :"short press" is switching cyclically "single / song" (no press function)

Packing included：
4 x Decoder player module

Note:
"long press" time is about 2S.
If you use U disk mode, some suggestions of 5V power supply, some U disk doesn't support 3.7V power supply.