principle using the head phone cable to touch off the photo button.
be attention before buying this product,pleas confirm the volume key of your phone can take pictues or set volume ley to take pictures.
aply to ios 5.0 above system,Adriod 4.2 above systam for ios systam you don't need to set up.
for Andriod systam you may set open your phone camera setting volume key set the volume key to take pictures.
some andriod phone can't be set,you can donload free APP like camera 360 to take pictures.