@TennisChamp59 That ding after takeoff means the landing gears are up and locked. You will also notice that the EMERGENCY EXIT signs will turn off. After 10,000 feet, depending on company procedures, we will switch off the seat belts signs or recycle them indicating to the light attendants that turbulence is expected.
Yea also if you notice another ding before landing, that is when the landing gear goes down, and the non-smoking sign was supposed to come on. Passing over 10000 ft is normally two or three dings, but in high altitude airport or bad conditions the dings dont ring until the plane is ok, for the the F/As to move around. Same happends when flying back to 10000ft, normally that has common PA such as: Flight Attendants prepare for landing.
@KDTWJetBlast Yes. It indicates that there is a 500 psi difference between the blue and yellow hydraulic systems. Once the systems senses a 500 psi difference it will automatically start the PTU to bring the psi within limits
I work with Airbus Planes, before all flights became non-smoking once you put up the landing gear, the non-smoking sign turned-off auto, but now that all flights are non-smoking, the ding still exists, but the sign remains on, during all the flight.