I maintain adherence to FCC guidelines on hybrid telcom systems- there is a novel full of performance benchmarks and technical parameters that I spend my life repairing, testing, setting up, documenting, rinsing, washing, and repeating on a bi-annual basis. Company parameters are much tighter, so FCC tests are never an issue.
I have spent 20 years doing this, leading to the next career- landlord. got a couple houses now and a few more bids in. once I hit my goal number of rental income per month, I retire. the goal is to do so before 45.