Cable terminators are required on ControlNet and DeviceNet networks to prevent reflections. Which statement best describes this?

• A. They are required on both
• B. They are never required
• C. They are required only on ControlNet
• D. They are optional

Answer: (A)

Signal reflections happen when a traveling pulse reaches the end of a transmission path that isn’t matched to the cable’s impedance. ControlNet and DeviceNet both use a bus-style network, so energy that isn’t absorbed will bounce back toward the transmitter and distort the next bits. Terminators provide a load that matches the cable impedance at the ends of the bus, absorbing the signal rather than reflecting it. Placing terminators at both ends keeps the signal clean across the network, reducing bit errors and timing issues. Some devices may include built-in termination that should be enabled only at the ends, but the important point is that termination is required at both ends to maintain reliable communication.