What is the primary advantage of relay contacts in control logic, enabling simultaneous output changes?

• A. They require less maintenance than solid-state devices
• B. They can turn some outputs on and others off at the same time
• C. They can operate without any wear
• D. They have faster response times

Answer: (B)

The main idea is that relay contacts can change multiple outputs at the same moment by being activated from a single coil. When the relay coil is energized, all the connected contacts switch together, so some outputs can turn on while others turn off in unison. This coordinated action is valuable in control logic because it prevents intermediate states where outputs change at different times, which could cause unsafe or undesired system behavior. The reason this is the best answer is that the inherent design of a relay uses a single actuation to drive many contacts, enabling true simultaneous output changes across those contacts.

As for the other options, relays aren’t inherently maintenance-free compared to solid-state devices, so claiming less maintenance isn’t universally true. Relays also wear from arcing and mechanical motion, so they don’t operate without wear. And while relays are reliable, they aren’t faster than solid-state switches, which typically offer quicker switching times.