Originally Posted by
island_airphoto
Is a loud buzzer that goes off at say 12,000 feet cabin pressure a thing?
The various Citation 550 and 560 models that I flew and fly have no audible warning for low cabin pressure. You get a flashing red warning light in the annunciator panel and a flashing red master warning light. Above 14.000 ft (plus minus a few) the passenger oxygen masks will drop automatically which may or may not be seen from the cockpit. There is no door, but some sort of divider and an optional curtain.