What is the primary characteristic of double-break contacts as described for Form Y?

Double-break contacts, as described for Form Y, are characterized by their mechanical linkage, which ensures that when one contact opens or closes, the other does as well. This characteristic is crucial for applications where reliability and synchronous operation of contacts are essential. The mechanical coupling helps to prevent scenarios where one contact might close while the other remains open, ensuring consistent performance in controlling electrical circuits.

The first option mentioning one actuator does not capture the unique feature of double-break contacts, which is their dual point of contact and interconnection. The second option discussing three contacts in series does not accurately depict the functioning of double-break contacts, which focus on the simultaneous operation of two contacts rather than incorporating additional contacts. The third option regarding SPDT (Single Pole Double Throw) contacts is also not applicable, as it refers to a specific type of contact with a different operational configuration than what is relevant for double-break contacts.

Thus, the defining aspect of double-break contacts, their mechanical linkage, is what sets them apart and provides specific advantages in certain electrical applications.