Final answer:
The exact minimum number of Passenger Service Units (PSC) for the CRJ 900 is not publicly disclosed, but each row of seats generally has a PSU for passenger services. Regulations and internal guidelines determine PSU configurations for safety and comfort.
Step-by-step explanation:
The PSC onboard aircraft supply minimum number for the CRJ 900 refers to the Passenger Service Units, which typically include individual air vents, reading lights, and flight attendant call buttons. Each row of seats on an aircraft is usually equipped with a PSU that services the passengers seated in that row. However, the exact minimum number of PSU's required on a CRJ 900 aircraft by regulation or manufacturer's design specifications is not publicly disclosed for proprietary or security reasons. Airlines and manufacturers may have internal guidelines that determine the configurations of their aircraft to ensure passenger safety and comfort while also complying with aviation authority regulations.