This contact structure consists of two blades that are not physically touching each other. This switch type is designated a "NORMALLY OPEN" contact because the blades are not touching one another when the lever is not activated. Moving the lever up (which is done mechanically in the switch) pushes the lower blade upward until it contacts the upper blade. Moving the lever back down will separate the two blades. When the blades are touching, the electrical circuit is "on". If they are not touching, the electrical circuit is "off".
This form also consits of two blades, constructed like "Form A" except the blades are touching each other before the lever has been moved. Since the electrical circuit is "on", moving the lever mechanically upwards causes the blades to open and turn the circuit "off". The designation is "NORMALLY CLOSED".
This form consists of three blades that combine the functions of both "Form A" and "Form B" type switches. The center blade is common to both "Form A" and "Form B" electrical circuits. Pushing the lever upward opens the lower blade (Form B) and closes the common blade with the upper blade (Form A).
Pushing the lever upward causes the bottom blade to meet with the top blade before the middle blade opens. Thus, it is designated as a "MAKE BEFORE BREAK" type switching function.
Pushing the lever upward causes the bottom blade to open first, meet the top blade second, and open the middle blade last. Therefore, this form is designated as a "BREAK BEFORE MAKE BEFORE BREAK".
This form has all blades "NORMALLY OPEN". The lever action is to both push and pull the center (common) blade. Pushing upward causes the common and upper blades to meet, while pushing downward causes the common blade to meet with the lower blade.
This form is the opposite of "Form F". By pushing the lever upwards, the contact between the middle and lower blade is broken. Pushing the lever downward will break the contact between the top blade and middle blade.
This form is "MAKE BEFORE MAKE" switch. Pushing the lever upward causes the lower blade to first contact the middle blade, then contact the upper blade.