What is the operation of Form D contacts during make-break?

The operation of Form D contacts during the make-break process is that they guarantee all terminals are connected. Form D contacts are designed to ensure that when the switch changes from one position to another, the connections that are supposed to be made are reliably completed without any interruption in the circuit. This guarantees a secure transition between the on (make) and off (break) states, preventing any momentary disconnection that could lead to equipment malfunction or system instability.

In contexts where multiple circuits or connections are handled, the robustness of Form D contacts is essential to maintain continuity and reliability in applications that require simultaneous operation across terminals. This means that during the transition, all necessary connections are maintained until the switch is securely in the new position, thereby creating a seamless operation.

Other options do not capture this critical function adequately. For instance, stating that connections are briefly opened before changing would not reflect the reliability expected from Form D contacts. Likewise, ensuring both connections are closed or keeping connections always closed does not accurately describe the operational nature of the contacts, which is focused on secure transitions rather than just open or closed states.