| 摘要 |
A relay system maintains an emergency door opening device circuit open so that a door of a structure remains closed as long as an electrically energized ventilation system of the structure is supplied with electrical energy from a commercial power source. When the power fails, the relay system closes the emergency door opening device circuit, which includes its own power source, to operate a door opening device which opens a door to the structure to provide emergency ventilation for the structure.
|
