|Manual wig wag|
Featured here is a low airpressure wig-wag. It seems that not everyone who has operated a truck with air brakes is familiar with them, though that are mentioned in the manuals. The deal is this. Every truck with air brakes is required to have a warning device to warn the operator if the air pressure becomes dangerously low. The two acceptable ways of doing that is with a low air warning buzzer that annoys the heck out of you when the pressure drops below 60 PSI, or with a WIG-WAG shown here which is mounted above the windshield and drops in front of your face under similar conditions.
This is a manual model shown in the 'warning' position. Once you start the truck and get up pressure, you can swing the flag to the right, and the air pressure will hold it up. Most trucks these days use the buzzer even though their value may be limited if the driver is hard of hearing or is wearing earplugs or the like due to high cab noise levels.