converted into the electrical current and is fed to the electrically controlled circuit such as a simple operational amplifier op amp based comparator the tir based optical touch switch can be operated into 2 modes depending on the design of the electrical control circuit one touch switch operation is the u201c touch on release off u201d or u201c touch off release on u201d mode another mode of touch switch operation is the u201c touch on touch off u201d or u201c touch off touch on u201d for the u201c touch off release on u201d switch operation when there is no fingertip 2 placed on the touching surface 13 of the tir based optical touch switch the electrical control box receives a constant electrical current as a result it will allow the desired electrical load to stay at the on state on the other hand when the fingertip 2 is placed on the touching surface 13 of the tir based optical touch switch the evanescent wave is coupled out of the triangle prism 4 through a thin layer of liquid on the fingertip 2 leading to the change of electrical current at the photodetector 3 if the electrical control box can sense this change of electrical current it will turn the desired electrical appliance to the off state the amount of changes in electrical current can be adjusted via the mechanical force applied on the touching surface 13 the surface roughness of the touching surface 13 the cross section area of the optical beam at the touching surface 13 the cleanness of the finger and.