Which term is not part of the catenary system's three main wires?

• A. Messenger
• B. Contact
• C. Hanger
• D. Indication

Answer: (D)

The main idea here is which items are the actual wires that form the overhead catenary system. In this setup, the messenger wire runs along the span under tension to provide support, the contact wire is the energized conductor that the train’s pantograph touches to draw power, and hangers are the supporting elements that suspend and correctly position the wires from the supporting structures. These three together are what keep the system functional and continuous along the line. Indication, on the other hand, is not a conductor or a supporting wire in the catenary; it refers to a signaling or status device. So it isn’t part of the three main wires.