If the master controller is moved to the ON position while the duplex gauge indicates 55 pounds, what happens?

When the master controller is moved to the ON position while the duplex gauge indicates 55 pounds, the train will remain stationary due to insufficient air pressure in the braking system. This low pressure situation means that the brakes are not fully released, which is a critical requirement for the train to move. The air pressure reading on the duplex gauge is essential for determining the state of the brake system; typically, a minimum pressure threshold must be met to allow the train to proceed. In this case, since 55 pounds is below the acceptable operating pressure, it prevents the release of the brakes, ensuring that the train stays halted and does not move. This is a safety mechanism to avoid any unintended movement when proper braking capability is not confirmed.