Final answer:
The deadman switch must be re-activated every 30 seconds during fueling operations with the Beta-Freightliner R-12 Hydrant-Servicing Unit.
Step-by-step explanation:
During fueling operations with the Beta-Freightliner R-12 Hydrant-Servicing Unit, the deadman switch must be re-activated, to prevent automatic shutdown, every 30 seconds.