As already commented, if you are drafting out of a lake or stream, you want strainers at the end of the intake line to keep from blocking the things up. The ones I remember had a couple of square feet of surface with quarter inch holes in it. The strainers at the truck are to protect the pump. (I've had them blocked up even on city water mains!)
It's been 25 years since I've been on the VFD but there was real high pressure (800 psi) booster lines that provided real "fog". I believe John Bean was the only company making them. They had a separate gear pump with "pump while in motion" ability. Those booster nozzles look like they could be that sort. If so, be very careful on straight stream, that pressure will go through a wall or through a hand very easily.
At least when I was in the service, all the main pumps were dual stage but only put out 150-170 psi or so max in pressure (series) mode, 100 psi in volume (parallel) mode. But I've never been around a truck with a front mount pump. As I recall, those were mainly on rural trucks where they had less water available and needed the midship space for more tank volume.
Yeah, that Q siren on the bumper is a real siren. Pulls around 225 amps after it gets wound up (not much different than a dead short.)
As I recall, for older equipment to remain in service and certified, it has to undergo an operational test running 24 hours at full rated capacity.
Ken
