What are the requirements for the direction of installation of electrical equipment switches

General switch installation to up for open, down for close. It is based on the premise of safety. In particular, the gate switch, if the switch down for the open (power state), then pull up for the closed state. In this way, in the case of the switch is pulled open, the switch may be under the action of gravity due to the vibration of the environment and automatically fall down, leaving the circuit in the on state. This will cause a safety accident!