A:

Good Morning,
NPSH = Straight Iron Pipe, also ID as IPT or SPIT
NST = National Standard Threads also ID as NH = National Hose. These 2 thread ID's are your most common FD threads nation wide, and are used as the standard, unless a town or city has it's own fire deppartment thread, ie New York City, Chicago,
you also had "NSH" we are not aware of this ID for hose thread