What is the key feature of Form K contacts?

The key feature of Form K contacts is that they have a center-off position. This design allows for a three-position mechanism where the contact can be in one of three states: closed, open, or in a neutral center-off position. This center-off position is particularly useful in applications where it is necessary to ensure that the circuit is completely de-energized while also providing an easy means to return to a closed or open state based on operational demands. Form K contacts facilitate more flexible operational scenarios, especially in control systems where both manual and automated switching needs are required.

The other options may describe features associated with various types of contacts, but they do not specifically reflect the primary characteristic of Form K contacts. Having a center-off position differentiates them from other contact types that may not have the same three-position functionality.