How many conductors are there in a signal main?

In a signal main, there are typically two conductors. This configuration is necessary to facilitate a complete circuit for the signaling system. The primary purpose of the conductors is to carry the electrical signals that manage the operation of railway equipment, such as signals and switches.

Having two conductors allows for a return path for the electrical current, enabling signals to be transmitted effectively between the control equipment and the signal devices. This dual conductor setup also helps ensure a stable and reliable signal transmission, as any disruption in one conductor can often be compensated for through the other, maintaining the integrity of the signaling system.

In contrast, options that suggest there are one, three, or four conductors do not align with standard practices in signaling systems, which rely on the two-conductor setup for safe and efficient operation.