The scales have a sensor that tells the attended someone drove up on to it. Get an axel on each scale, then shut off the truck so you can hear...feel free to get out if you need to get nearer the speaker to hear/talk.
Attendant: "First weigh?"
You: "Yes"
Attendant: "Company name?"
You: "Bily Bob's RV"
Attendant: "Truck Number?"
You: "one"
Attendant: "Trailer?"
You: "one"
Attendant: "OK, come inside"
You pull off scale, go drop trailer, come back with just the truck.
Attendant: "First weigh?"
You: "re-weigh"
Attendant: "company"
You: "Billy Bob's RV"
Attendant: "come inside"
Some even have a camera, so if they see it is an RV, they may just tell you they got it, come inside.
Do not be surprised if they seem short & to the point. They are busy dealing with fuel pumps, a convienent store, etc... They are use to dealing with professionals who do not want their time wasted.
Whatever you do, do NOT block the scale. Get on, get off, park out of the way.