an electronic device that you can use to hear and sometimes see a child who is in a different room

For us a baby monitor is a necessity as we live in a big house and can't hear the baby crying in her room. 婴儿监护器对我们来说是必不可少的，因为我们住在一幢大房子里，宝宝在自己房间里哭的话，我们是听不见的。