活动装置 meaning in English

flexible installation
mobile plant
movable equipment

Open the shell by one pressing
一次按压，活动装置可慢慢打开。
A movable structure used to close off an entrance , typically consisting of a panel that swings on hinges or that slides or rotates
门一种用于关闭入口活动装置，典型的由一块板上有铰链转动或为拉动式或为旋转式的组合
The most popular ones had moving parts : little birds perched on a spring seemed to fly , doors and windows opened to reveal the sweet verse
其中最流行的一种还带有活动装置：栖息于一个弹簧上的小鸟跃跃欲飞，若打开其中的门窗还可呈现出甜蜜的诗文。