DB- 3- 4型全自动防火门闭门器是北京长城无线电厂开发的最新产品。该产品采用微型电磁阀,功耗低,可靠性高,并带有信号反馈插座,可与消防智能控制系统联网,实现公共场所建筑内防火门的常开与自动关闭。使用该闭门器可以避免防火门常闭给人们带来的通行不便,又能实现防火门应急 DB-3- 4-type automatic fire door closer is the latest product developed by Beijing Great Wall Radio Factory. The product uses a miniature solenoid valve, low power consumption, high reliability, and with a signal feedback socket, fire intelligent control system can be networked to achieve public buildings in the building often open and automatic fire doors closed. The use of the door closer can avoid the usual closed-door fire to the inconvenience caused by people, but also to achieve fire door emergency