Before the laser, scientists developed a similar device: a maser which stands for Microwave Amplification by Stimulated Emission of Radiation.

VOA: special.2010.09.01

Not just an amplification system that you put in your ear, but actually an implant that replaces the function of an organ inside your ear.

人工耳蜗不是一个简单的,植入耳朵的扩音系统,而是一种,能替代听力器官功能的移植物

耶鲁公开课 - 生物医学工程探索课程节选

Until the teens, telephones were very expensive because they didn't have good amplification technology.

在20年代之前,电话还是奢侈品,因为它们还没有增强讯号技术

耶鲁公开课 - 金融市场课程节选