What is a possible signal for low air pressure in the system?

A red light, a wig wag mechanical arm, or a buzzer are all designed to alert the driver of low air pressure in the brake system. These signals are critical safety features in commercial vehicles equipped with air brakes, as they indicate that the braking capacity may be compromised if air pressure falls below a safe level.

The red light serves as a visual cue, while the wig wag mechanical arm, which moves back and forth, provides a more immediate, attention-catching indication of the issue. A buzzer adds an audible alert to ensure that the driver is made aware of the situation promptly.

These mechanisms are essential to ensure that drivers do not overlook potential braking issues, thereby maintaining safety on the road. Other options might indicate different types of alerts or issues, but the specific combination mentioned directly pertains to low air pressure in the air brake system.