The contacts of 24vdc relay have three basic forms:

1. The two contacts of the moving close (normally open) (H type) coil are disconnected when the coil is not energized, and the two contacts are closed after energization. It is represented by the pinyin prefix "H" of the ligature.

2. The two contacts of the dynamic break type (normally closed) (D type) coil are closed when the coil is not energized, and the two contacts are disconnected after energization. It is represented by the word-breaking pinyin prefix "D".

3. Conversion type (Z type) This is the contact group type. This contact group has three contacts in total, that is, a moving contact in the middle, and a static contact at the top and bottom. When the coil is not energized, the movable contact and one of the static contacts are disconnected and the other is closed. After the coil is energized, the movable contact moves, making the original disconnected to be closed, and the originally closed to be in an open state to achieve the conversion. Purpose. Such a set of contacts is called a changeover contact. It is represented by the pinyin prefix "z" of the word "turn".